Its a bell & whistle type item that is not nessessary for the ski to function. If you decide to buy one, get a plastic one. I never shut mine off unless I am serviceing the fuel system. The part receives two lines from the fuel tank, RES is a bottom of
the tank straw, ON is a straw 2" higher up in the tank. Use of the valve may get you to saftey should the operator neglect the fuel level. Hope this helps! Bills86e