Interstate Pneumatics LF10-4H is a 4 port 85-125 PSI air compressor pressure switch with unloader control valve and On / Off switch. This pressure switch is designed for a single stage or two stage air compressor pumping up to 125 PSI. This switch features a built-in On / Off metal lever and also a unloader located on the side of the switch. The unloader is used to unload head pressure off the compressor pump for a load free start up. If your compressor does not require an unloader valve on the pressure switch you can leave it not hooked up and the switch will still function properly. The four-port manifold gives you the option to mount in it any direction and to also have the option to add a relief valve, gauge, or multiple air outlet ports. This switch comes preset to turn the compressor on at 85 PSI and shut off at 125 PSI . This can be adjusted to any pressure within the factory minimum and maximum set points listed below