This is a gas or fuel tank switch over or selector valve.
It allows you to run two separate fuel tanks and only draw off of one tank at a time.
You would run one fuel line from each tank to the valve and a line from the valve to your engine.
For a switch you could use a common toggle or rocker switch.
Has 5/16" hose barbs and works off of 12 volt DC.
. Intended for use with the following:
Vehicles with one main and one auxiliary fuel tank.
GENUINE: STANDARD MOTOR PRODUCT
IN ORIGINAL BOX
12 Volt systems.
Can be used for either gasoline or diesel fuels.
Located between the Fuel Pump and the Fuel Tank
*