I'm looking for a discontinued part. An air actuated, top of head mounted, unloader, made in the 60's and 70's. It's a simple 1.5" x 3" piece of steel that has 2 (pistons) valves with stems that press down on the intake flapper valves in the compressor and unload the air pressure thus allowing the air compressor to continue running "freewheel". These are fairly indestructible. It's mounted with 4 small screws from the top down into the compressor head. It fits campbell H-speedaire-dayton-sears & several others.... typical 2 3/4", upright twin piston, single stage, 11cfm ....... here's a link : Model # 106175110 Parts.Sears.Com ( Parts 1A thru 1G )