This standard covers reinforced and flexible hoses intended for use in water and ethylene glycol based engine coolant system application. (SAE 20R1): Heavy-duty type for service in heavy-duty application. This type is available in two wall thicknesses as indicated in paragraph 4.3. (SAE 20R2): Flexible heavy-duty wire embedded type for the same service as SAE 20R1. (SAE 20R3): Heater hose for normal service. (SAE 20R4): Radiator hose for normal service. (SAE 20R5): Covoluted wire supported type for normal service@. (SAE 20RXHT): New-any hose type SAE 20r1- SAE 20R5 which is required to operate in an environment of above 125C. Compounds based on different synthetic rubber grades are specified and designated Class A@ high temperature resistant; Class B@ high oil swell resistant; Class A@ high temperature resistant; class B@ high oil swell resistant; Class C@ medium oil swell resistant; Class D-1@ low oil resistant@ improved service; Class D-2 low oil resistant@ standard service; Class D-3 low oil resistant@ high temperature resistant@ premium service; Class E@ low oil resistant@ fiber elastomeric composite. Typical physical characteristics for each type hose