30R7 is the hose carrying fuel from the tank to the fuel pump.  Works well in applications at 50 psi working pressure up to 3/8".  Good for 35 psi over 3/8".

J1527 marine exhaust hose is suitable for exhaust gas from water cooled stationary or marine diesel engines.

The transfer hose is good for gasoline and other petroleum based products under pressure, gravity flow or full suction.