Coolant Hoses - Engine Bay

Breather hose - Coolant expansion tank.

Fits:
Porsche 997.1 Turbo 2007-09
Porsche 997 GT3 2007-09

Click 'Zoom in' for large parts diagram.
Diagram ref no 16

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99710625101

The product you are viewing cross references to these numbers

Breather hose - Coolant expansion tank.

Fits:
Porsche 997.1 turbo - 2007 to 2009
Porsche 997 GT3 - 2007 to 2009

Click 'Zoom in' for large parts diagram.
Diagram ref no 16

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99710625101

The product you are viewing cross references to these numbers

BBi Autosport billet aluminium coolant pipe repair kit

Fits
Porsche 997 Gen 1 Turbo
Porsche 997 Gen 1 GT2

Coolant pipe failure is an inevitable problem with the Porsche GT1-block equipped models (GT3, GT2, Turbo).
Bonded together by adhesives, the factory pipes will eventually leak or abruptly fail. As the best preventative fix and solution for this problem, BBi Autosport offers replacement billet aluminum coolant pipes to be permanently welded in place.
Compared to the factory fittings, these replacement billet fittings offers superior metallurgy to allow stronger, higher quality welds.

Extensive surface preparation and welding skills are required to properly weld the fittings.

The engine requires removing and the necessary components disassembled and thoroughly cleaned, ideally in a ultrasonic cleaner.
Afterwards, the pipes need to be meticulously welded into place and pressure tested for leaks prior to reinstalling the engine.

Coolant return pipe.

Fits:
Porsche 997.1 Turbo 3.6L / GT2 2007-09
Porsche 997.2 GT2 RS 3.6L 2010-13

Click 'Zoom in' for large parts diagram.
Diagram ref no 4

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99710625474

The product you are viewing cross references to these numbers

Coolant Supply Hose.

The Genuine Porsche Coolant Supply Hose 99710647772 is an original equipment replacement cooling system component designed for selected Porsche 911 (997) Turbo, GT2, GT2 RS, GT3 and GT3 RS models.

Fits:

• Porsche 997 MK1 TURBO 2007-09
• Porsche 997 MK1 GT3 / GT3 RS 2007-09
• Porsche 997 MK1 GT2 2007-09
• Porsche 997 MKII GT3 / GT3 RS 2010-11
• Porsche 997 MKII Turbo 2010-13
• Porsche 997 MKII GT2 RS 2011-13  

Diagram Ref No 32

Manufactured to Porsche's original specifications, this coolant hose connects the water pump housing to the coolant supply pipe, helping maintain reliable coolant circulation and effective engine temperature regulation.

The hose forms an essential part of the engine's liquid cooling system, providing a secure and flexible connection between cooling circuit components. It is designed to withstand the temperature changes, pressure fluctuations and vibration experienced during normal engine operation.

Over time, exposure to engine heat, coolant pressure and general ageing can cause the original hose to become hardened, swollen, cracked or weakened, potentially resulting in coolant leaks and reduced cooling system reliability.

The Genuine Porsche Coolant Supply Hose provides a direct original equipment replacement solution, helping restore the integrity of the cooling system while maintaining the correct hose routing and connection arrangement.

Ideal for routine cooling system maintenance, water pump repairs and engine refurbishment, this component helps protect the engine against coolant loss and overheating.

What This Product Does:
The coolant supply hose connects the engine's water pump housing to the coolant supply pipe, providing a sealed passage through which coolant circulates within the engine cooling system.

Its key functions include:

• Coolant Circulation: Allows coolant to flow between the water pump housing and the connected coolant supply pipe.
• Engine Temperature Regulation: Supports the cooling system's ability to maintain the engine within its intended operating temperature range.
• Secure Cooling System Connection: Provides a reliable connection between designated cooling system components.
• Leak Prevention: Helps maintain a sealed cooling circuit, reducing the risk of coolant escaping.
• Cooling System Pressure: Supports the integrity of the pressurised cooling system during normal operation.
• Thermal Resistance: Designed to withstand engine heat and repeated temperature fluctuations.
• Vibration Accommodation: Provides a flexible connection that accommodates normal engine vibration and movement.
• Overheating Prevention: Helps maintain sufficient coolant circulation to support effective engine cooling.
• Engine Protection: Reduces the risk of cooling-related damage by maintaining a dependable coolant flow path.
• Original Equipment Fitment: Maintains Porsche's specified hose dimensions, routing and connection arrangement.

Symptoms Of Wear Or Failure:
Over time, continuous exposure to engine heat, coolant pressure, vibration and ageing can cause coolant supply hoses to deteriorate.

Common signs include:

• Visible Coolant Leaks: Coolant dripping beneath the vehicle or collecting around the water pump housing may indicate a damaged or leaking hose.
• Low Coolant Warning: Coolant escaping from a worn hose may cause the reservoir level to fall, triggering a dashboard warning.
• Frequent Coolant Top-Ups: Repeatedly needing to refill the coolant reservoir may indicate a leak within the cooling system.
• Cracked or Split Hose Material: Visible cracks, splits or surface deterioration may indicate ageing or weakening of the hose.
• Swollen or Bulging Hose: Internal deterioration or abnormal cooling system pressure may cause the hose to expand or deform.
• Hardened or Brittle Rubber: Repeated exposure to high temperatures may reduce flexibility and increase the risk of cracking.
• Soft or Spongy Sections: Localised weakening of the hose structure can indicate internal deterioration.
• Coolant Residue Around Connections: Dried coolant deposits or staining around the hose ends may indicate previous or ongoing leakage.
• Coolant Smell from the Engine Bay: Escaping coolant may produce a distinctive sweet smell, particularly when contacting warm engine components.
• Engine Overheating: Significant coolant loss can reduce the cooling system's ability to regulate engine temperature.
• Fluctuating Engine Temperature: Coolant loss or air entering the cooling system may contribute to unstable temperature readings.
• Steam from the Engine Compartment: A severe coolant leak may allow coolant to contact hot engine components, producing visible steam.
• Loose or Damaged Hose Connections: Deteriorated clamps or damaged connection surfaces may allow coolant to escape.

Why Replacement Matters:

• Replacing a worn, leaking or damaged coolant supply hose is essential for maintaining the reliability, performance and long-term protection of your Porsche's engine cooling system.
• The engine cooling system relies on the continuous circulation of coolant through a sealed network of hoses, pipes and associated components. The coolant supply hose plays an important role by maintaining a secure connection between the water pump housing and the coolant supply pipe.
• As the original hose ages, repeated heating and cooling cycles can cause the material to lose flexibility, develop cracks or weaken around its connection points.
• Even a small coolant leak can gradually reduce the coolant level, limiting the system's ability to control engine temperature effectively.
• If the hose deteriorates further or fails suddenly under pressure, rapid coolant loss may occur, potentially resulting in engine overheating and an unexpected breakdown.
• Overheating can cause serious damage to internal engine components, including cylinder heads, gaskets and associated cooling system parts.
• A correctly fitted Genuine Porsche replacement hose helps restore the original cooling system connection, ensuring appropriate fitment, routing and sealing performance.
• Maintaining reliable engine cooling is particularly important for high-performance Porsche Turbo, GT2 and GT3 models, where the engine can experience substantial thermal loads during demanding driving conditions.
• Replacing deteriorated hoses during water pump servicing or major cooling system maintenance can also help prevent recurring leaks and reduce the likelihood of more expensive repairs.
• The genuine replacement maintains the original equipment configuration, making it suitable for Porsche owners who wish to preserve factory-standard component quality and fitment.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99710647772

The product you are viewing cross references to these numbers

Coolant supply line for the turbocharger. 

Fits:
Porsche 997-1 Turbo / GT2 2007-09 
Porsche 997-2 GT2 RS 2011-13

Diagram reference(s):

No. 11 - Cylinders 1-3
No. 12 - Cylinders 4-6

NOTE: Our product image shows 99710607379, which is for cylinders 1-3.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99710607

The product you are viewing cross references to these numbers

Cooling Water Tube - Return Line.

Fits:
Porsche 997 MKI Carrera All.
997 Carrera 2 3.6L 2005>>
997 Carrera 2S 3.8L 2005>>
997 Carrera 4 3.6L 2005>>
997 Carrera 4S 3.8L 2005>>
Porsche 997 MKI Turbo

Porsche 997 MKII Carrera All. 2009>>
997 Carrera 2 3.6L 2009>>
997 Carrera 2S 3.8L 2009>>
997 Carrera 4 3.6L 2009>>
997 Carrera 4S 3.8L 2009>>
Porsche 997 MKII Turbo 2009>>

Diagram Ref no 7

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99710680902

The product you are viewing cross references to these numbers

Heater hose - Engine to return line.
Genuine Porsche Original Equipment (OE) heater coolant return hose that connects between the engine cooling circuit and the heater return line, ensuring proper coolant flow through the heater core and back to the engine cooling system.

Fits:
Porsche 996 Carrera 2002 - 2005 Tiptronic Gearbox only
Porsche 997.1 3.6L / 3.8L 2004 - 2008
Porsche 997.1 Turbo / GT2 2007 - 2009
Porsche 997.2 Turbo / GT2 RS 2010 - 2013
Porsche 997 GT3 3.8 / 4.0 2009 - 2011

Diagram ref no 42

This hose ensures an unobstructed and secure channel for coolant returning from the vehicle’s heater core to the engine cooling loop, playing a vital role in passenger cabin heating and overall engine thermal regulation. Its precise fit and correct routing are essential to avoid bypassing or pinching, which could otherwise lead to heater inefficiency or premature failure.

Installed between the heater core outlet and the engine’s return fitting, this hose:
• Transports heated coolant from the heater core back to the engine cooling system
• Maintains correct flow and pressure balance within the cooling circuit
• Operates under high temperatures and multiple thermal cycles
•  Interfaces with factory-specified clamps and hose connections
Because it is made to OE specification, the hose ensures proper sealing and routing that matches the original Porsche design.

A cooling system hose that has become brittle, cracked, swollen, or porous can leak or restrict flow, leading to reduced heating performance, coolant loss, and potential engine overheating. Because the heater return hose carries pressurised coolant across temperature extremes, degradation over time is typical. Replacing it with a Genuine Porsche OE part ensures correct material performance and sealing, helping preserve cooling efficiency and prevent unexpected failures.

When to replace:
•  Visible cracks, swelling, or soft spots
•  Coolant leaks around the hose ends
•  Heater blowing cold air, indicating poor coolant flow
•  Cooling system overhaul or heater core service
•  Preventive maintenance on high-mile vehicles

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99610622275

The product you are viewing cross references to these numbers

Heater hose - Engine to return line.
OE Match heater coolant return hose is a direct-fit replacement designed to replicate the original Porsche hose used in the heater return circuit on Porsche 911 996 and 997 models. It carries coolant from the heater core back into the engine cooling system, supporting both cabin heating and overall thermal regulation.

Fits:
Porsche 996 Carrera 2002 - 2005 Tiptronic Gearbox only
Porsche 997.1 3.6L / 3.8L 2004 - 2008
Porsche 997.1 Turbo / GT2 2007 - 2009
Porsche 997.2 Turbo / GT2 RS 2010 - 2013
Porsche 997 GT3 3.8 / 4.0 2009 - 2011

Diagram ref no 42

The hose installs directly using original mounting points and standard Porsche hose clamps, making it suitable for both routine maintenance and larger cooling system overhauls.

The heater coolant return hose channels warmed coolant from the heater core back to the engine’s cooling circuit, completing the heater loop. This allows the cooling system to maintain balanced flow and ensures consistent interior heating performance.

Installed between the heater core outlet and the engine return line, this hose:
•  Maintains correct coolant flow and pressure in the heater circuit
•  Supports reliable cabin heating
•  Resists collapse, swelling, and heat degradation
•  Integrates with factory hose routing and connections
 Its OE-matched geometry ensures proper clearance and reduces stress on joints and adjacent hoses.

Over time, heater hoses deteriorate due to heat cycling and coolant exposure. A failing return hose can cause coolant leaks, reduced heating efficiency, air ingress into the cooling system, or engine overheating. Replacing worn hoses with an OE Match component restores proper coolant circulation and helps prevent unexpected cooling system failures.

When to replace:
•  Visible cracks, swelling, or soft spots
•  Coolant leaks around the hose ends
•  Heater blowing cold air, indicating poor coolant flow
•  Cooling system overhaul or heater core service
•  Preventive maintenance on high-mile vehicles

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99610622275

The product you are viewing cross references to these numbers

Heater Supply Hose. 

The Genuine Porsche Heater Supply Hose 99710623372 is an original equipment replacement cooling and heating system component designed for selected Porsche 911 (997) Turbo, GT2, GT2 RS, GT3 and GT3 RS models.

Fits:

• Porsche 997 MK1 TURBO 2007-09
• Porsche 997 MK1 GT3 / GT3 RS 2007-09
• Porsche 997 MK1 GT2 2007-09
• Porsche 997 MKII GT3 / GT3 RS 2010-11
• Porsche 997 MKII GT2 RS 2011-13  

Diagram Ref No 1

Manufactured to Porsche's original specifications, this heater supply hose forms part of the vehicle's coolant heating circuit, helping transport heated engine coolant through the designated heater supply pipework to support effective cabin temperature regulation.

Also known as a heater coolant supply hose or HVAC heater hose, this component provides a flexible, sealed connection within the heating system, allowing coolant to circulate under normal operating temperatures and pressure.

The hose is designed to withstand repeated heating and cooling cycles, engine vibration and the pressure changes experienced within the cooling system.

Over time, exposure to coolant, engine heat and general ageing can cause the original hose to deteriorate, potentially resulting in cracks, swelling, coolant leakage or weakened connections.

The Genuine Porsche Heater Supply Hose provides an original equipment replacement solution, helping restore the integrity of the heating circuit while maintaining the correct factory hose routing and connection arrangement.

Ideal for routine cooling system maintenance, heater circuit repairs and engine refurbishment, this component helps maintain reliable coolant circulation, efficient heating performance and long-term cooling system integrity.

What This Product Does:
The heater supply hose forms part of the engine's coolant-based heating system, providing a sealed passage for heated coolant to circulate through the designated heater supply circuit.

By maintaining reliable coolant flow, the hose supports the vehicle's heating system and helps preserve the integrity of the pressurised cooling circuit.

Its key functions include:

• Heater Coolant Supply: Carries heated coolant through the designated supply section of the vehicle's heating circuit.
• Cabin Heating Support: Helps provide the coolant flow required for effective cabin heating and temperature regulation.
• Cooling System Circulation: Maintains a continuous coolant passage between the connected heating system components.
• Secure Hose Connection: Provides a reliable flexible connection within the heater supply pipework.
• Leak Prevention: Helps maintain a sealed coolant circuit, reducing the risk of coolant escaping.
• Cooling System Pressure: Supports the integrity of the pressurised engine cooling and heating system.
• Thermal Resistance: Designed to withstand repeated exposure to heated engine coolant and temperature fluctuations.
• Vibration Accommodation: Provides flexibility to accommodate normal movement and vibration between connected components.
• Engine Cooling Support: Helps maintain the integrity of the wider engine cooling system by preventing coolant loss.
• Original Equipment Fitment: Maintains Porsche's specified hose dimensions, routing and connection configuration.

Symptoms Of Wear Or Failure:
Over time, repeated thermal cycling, coolant pressure, vibration and ageing can cause heater supply hoses to weaken or deteriorate.

Common signs include:

• Visible Coolant Leaks: Coolant escaping around the hose or its connections may indicate cracking, damage or a failed seal.
• Low Coolant Warning: A leaking heater supply hose may cause coolant levels to fall, triggering a dashboard warning.
• Frequent Coolant Top-Ups: Repeated coolant loss may indicate deterioration within the hose or another cooling system component.
• Cracked or Split Hose Material: Visible cracks, splits or surface deterioration may indicate that the hose is approaching the end of its service life.
• Swollen or Bulging Hose: Internal material deterioration or excessive cooling system pressure may cause the hose to expand or deform.
• Hardened or Brittle Rubber: Repeated heat exposure can reduce flexibility and increase the likelihood of cracking.
• Soft or Spongy Sections: Localised weakening of the hose structure may indicate internal material deterioration.
• Dried Coolant Residue: Deposits or staining around the hose connections may indicate previous or ongoing leakage.
• Reduced Cabin Heating Performance: Significant coolant loss or air entering the heating circuit may affect cabin heater operation.
• Fluctuating Heater Temperature: Air trapped within the cooling circuit may cause inconsistent heating performance.
• Coolant Smell: Escaping coolant may produce a distinctive sweet smell around the affected area.
• Engine Overheating: Substantial coolant loss can reduce the overall cooling system's ability to regulate engine temperature.
• Steam from the Engine Compartment: A significant coolant leak may allow coolant to contact hot components, producing visible steam.
• Loose or Damaged Hose Connections: Corroded clamps or damaged connection surfaces may allow coolant to escape.

Why Replacement Matters:

• Replacing a worn, leaking or damaged heater supply hose is essential for maintaining the reliability, efficiency and integrity of your Porsche's heating and cooling system.
• The heater supply circuit relies on a secure passage for heated engine coolant to circulate between its associated components. If the supply hose becomes cracked, swollen or weakened, coolant may escape, reducing the system's ability to maintain correct coolant levels and pressure.
• Even a small coolant leak can develop into a more serious problem, particularly as the hose undergoes repeated heating and cooling cycles.
• As coolant levels fall, air may enter the system, potentially affecting heater performance and contributing to inconsistent temperature regulation.
• If the hose deteriorates further and fails under pressure, sudden coolant loss may occur. This can increase the risk of engine overheating and potentially lead to costly damage to cylinder heads, gaskets and other critical engine components.
• A correctly fitted Genuine Porsche replacement hose helps restore a secure, leak-resistant connection and maintain the original heating circuit configuration.
• Replacing deteriorated hoses during routine servicing or cooling system repairs can also help prevent unexpected breakdowns and reduce the likelihood of additional damage to surrounding components.
• For high-performance Porsche 997 Turbo, GT2 and GT3 models, maintaining cooling system integrity is particularly important because the engines can experience substantial thermal loads during demanding driving conditions.
• The genuine replacement hose provides the correct factory-style routing and connection arrangement, making it suitable for owners who wish to maintain original equipment quality and compatibility.
• The Genuine Porsche Heater Supply Hose 99710623372 offers an original equipment replacement solution designed to restore reliable coolant circulation, maintain cabin heating performance and help protect the engine against coolant loss and overheating.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99710623372

The product you are viewing cross references to these numbers

O-ring 39,20 x 3,00 water cooling. 

Fits:
Porsche 996 turbo - 2000 to 2005
Porsche 996 GT3 - 1999 to 2004
Porsche 997.1 turbo - 2007 to 2009
Porsche 997 GT3 - 2007 to 2011
Porsche Carrera GT - 2003 to 2006
Porsche 918 Spyder

Diagram ref no 14

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99970741040

The product you are viewing cross references to these numbers

O-ring 39,20 x 3,00 water cooling
This OE match O-ring is a direct replacement for the original Porsche sealing ring used within the water cooling systems of Porsche 996 Turbo, 996 GT3, 997 Turbo, and 997 GT3 models. Manufactured to OE specifications, it features precise dimensions of 39.20mm x 3.00mm to ensure correct sealing performance and factory-style fitment.
Sold individually

Fits:
Porsche 996 turbo - 2000 to 2005
Porsche 996 GT3 - 1999 to 2004
Porsche 997.1 turbo - 2007 to 2009
Porsche 997 GT3 - 2007 to 2011
Porsche Carrera GT - 2003 to 2006
Porsche 918 Spyder

Diagram ref no 14

Proper sealing within the cooling system is essential for maintaining coolant pressure and preventing leaks that could lead to overheating or engine damage. OE Match construction ensures compatibility with original Porsche cooling system components and reliable sealing performance under demanding operating conditions.

Ideal for preventative maintenance, cooling system servicing, or engine rebuild work, this O-ring helps restore proper sealing integrity and reliable coolant circulation.

The O-ring creates a pressure-tight seal between cooling system components, preventing coolant leaks and maintaining correct cooling system pressure. It helps ensure efficient coolant circulation and reliable engine temperature control.

Function
• Seals coolant system connections and housings
• Prevents coolant leakage under pressure
• Maintains correct cooling system pressure
• Supports reliable engine temperature regulation
• Resists heat, coolant exposure, and pressure cycling

Cooling system O-rings harden and lose elasticity over time due to heat exposure, coolant chemicals, and pressure cycling. A deteriorated seal can cause coolant leaks, pressure loss, overheating, and potential engine damage. Replacing worn O-rings during servicing helps maintain cooling system integrity and prevents costly repairs.

When to replace
•  Coolant leaks around sealed connections
•  During cooling system disassembly or servicing
•  Signs of flattened, cracked, or hardened seals
•  Loss of coolant pressure
•  During engine rebuild or preventative maintenance

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99970741040

The product you are viewing cross references to these numbers

O-ring – 46.7 x 3.53 – used in various applications within the car's cooling system.

Fits:
Porsche 987 Boxster 2005-12
Porsche 987 Cayman 2006-12

Porsche 981 Boxster 2012-16 
Porsche 981 Boxster Spyder 2016 
Porsche 981 Cayman 2014-16 
Porsche 981 Cayman GT4 2016 

Porsche 718 (982) Boxster 2017>> 
Porsche 718 (982) Boxster Spyder 2019>>
Porsche 718 (982) Cayman 2017>>
Porsche 718 (982) Cayman GT4 2019>>

Porsche 996 GT3 / RS 1999-05
Porsche 996 Turbo / GT2 2001-05

Porsche 997 Carrera 2005-12
Porsche 997 Turbo / GT2 RS 2007-13
Porsche 997 GT3 / RS 2007-11

Porsche 991 Carrera 2012-19
Porsche 991 Turbo / GT2 RS 2014-20
Porsche 991 GT3 / RS 2014-21

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99610680103

The product you are viewing cross references to these numbers

O-ring – 46.7 x 3.53 – used in various applications within the car's cooling system.

Fits:
Porsche 987 Boxster 2005-12
Porsche 987 Cayman 2006-12

Porsche 981 Boxster 2012-16 
Porsche 981 Boxster Spyder 2016 
Porsche 981 Cayman 2014-16 
Porsche 981 Cayman GT4 2016 

Porsche 718 (982) Boxster 2017>> 
Porsche 718 (982) Boxster Spyder 2019>>
Porsche 718 (982) Cayman 2017>>
Porsche 718 (982) Cayman GT4 2019>>

Porsche 996 GT3 / RS 1999-05
Porsche 996 Turbo / GT2 2001-05

Porsche 997 Carrera 2005-12
Porsche 997 Turbo / GT2 RS 2007-13
Porsche 997 GT3 / RS 2007-11

Porsche 991 Carrera 2012-19
Porsche 991 Turbo / GT2 RS 2014-20
Porsche 991 GT3 / RS 2014-21

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99610680103

The product you are viewing cross references to these numbers

Protective Ring For Engine Coolant Pipe.
Sold Each.
x2 Required Per Car.

Fits:
Porsche 996 Turbo / GT2 2001>>2005
Porsche 996 GT3 1999>>2005
Porsche 997.1 Turbo / GT2 MKI 2007>>2009
Porsche 997.1 GT3 MKI 2007>>2009
Porsche 997.2 Turbo / GT2 RS MKII 2010>>2013
Porsche 997.2 GT3 MKII 2010>>2011

Diagram Ref No 16

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99610621470

The product you are viewing cross references to these numbers

Water coolant hose return. 

Fits:
Porsche 997.1 turbo - 2007 to 2008
Porsche 997.2 GT2 - 2001 to 2012
Porsche 997 GT3 - 2007 to 2012

Click 'Zoom in' for large parts diagram.
Diagram ref no 2 or 45

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99710632872

The product you are viewing cross references to these numbers