This is the green plastic hose that fits on the overflow tube below the neck of the radiator and directs the overflowing water away from the wiper motor and engine bay. Sold per metre only.
Also used as expansion tank hose on very early leyland cars.
GRH1005M was the original rubber hose with 15/32"internal bore size but was replaced with plastic by Rover.
LPH630 hose will fit if you want a more substantial rubber hose .