New Four Seasons manual heater valve.  This valve is for 5/8" ID heater hose.  This valve would be spliced in one of your heater hoses to prevent coolant from flowing through the heater core.  Blocking your heater core flow will provide better A/C cooling on vehicles not equipped with a heater core bypass valve.  This is a manual valve, meaning you need to turn the valve open and closed by hand as needed.  This can also be used to block off a leaking heater core, however, 2 valves are required to stop a leak as both heater core hoses need to be blocked (one hose is usually 5/8", the other is usually 3/4").  Valve is sold individually.  Overall size is roughly 2 1/2" x 2 1/2" x 5/8" thick. 

Universal applications.