Brand new 1/2 npt by 1/2 compression air compressor in tank check valve, with 1/8 female npt threads on the side for un-loader port. Check valves are used to prevent backflow of air. This style is used to directly screw into the air tank and keep pressure from leaving the tank and putting pressure against the compressor pump once the compressor is shut off. This item is made in the united states by CONRADER CO.