Must order quantity of 4 for complete set. 

Old Part Numbers: CAC-437Check Valve, 1/2" compression x 1/2" male NPT. The check valve is a one-way valve that prevents air from backfeeding from the air tank. If the small unloader (bleeder) valve on or under your switch leaks constantly AFTER the unit...

Old Part Numbers: 69DCAUnloader valve used on many Furnas/Hubbell brand air compressor pressure switches; includes the unloader valve with compression nut and sleeve, and screw. Replace this part if it leaks while the unit is running. If this part leaks...