SAE 20R3 Class D-2. SAE 20R3 Class A. [Size] ID: 5/8" (16mm), tolerance is ±0.5mm; OD: 0.94" (24mm), tolerance is ±0.6mm; Length: 50 feet. [Application] Used in hot water heater, engine's cooling system, connecting the radiator to the overflow reservoir, etc.
