It is the Society of Automotive Engineers standard for coolant and heater hose. R3 designates a heavy-duty, reinforced hose suitable for engine coolant service - the specification the great majority of original-equipment radiator and heater hoses are built to. When a hose carries this rating you know its construction, temperature capability and pressure margin have been tested to a recognised benchmark.

Everything in our range built to that standard - silicone straights, elbows in all four angles, reducers, reducing elbows, couplers, continuous coil hose and wire reinforced SuperFlex, plus rubber radiator and heater hose, moulded rubber elbows and coupling joiners, and the vehicle-specific coolant and intercooler hoses and kits that use J20 R3 material.

Our silicone hose to this standard runs -50C to +250C continuously, with working pressures from around 12.33 bar on the smallest bores down to 2.8 bar on the largest and burst up to 37 bar. Rubber hose to the same standard runs -30C to +120C. Both are glycol rated for standard antifreeze mixes.

No. J20 R3 is a coolant and heater specification - both the silicone and the EPDM rubber versions swell and degrade in contact with petrol, diesel and oil. For hydrocarbons you need SAE J30 R6 hose, which is our fluorolined silicone and our rubber fuel and oil range. Check the specification on the product page before you order.

No - the standard covers construction and performance, not dimensions. Order by internal diameter, matched to the outside diameter of the pipe stub the hose slides onto. Measure the pipe with vernier callipers rather than the old hose, which will have stretched in service and reads larger than the pipe it was on.

Both meet the standard; they differ in service life and temperature headroom. Rubber to J20 R3 is the like-for-like replacement at lower cost and runs to +120C. Silicone to the same standard runs to +250C and does not perish or harden with age. For a standard vehicle rubber is correct; for a hot-running or hard-to-access application, silicone.