Brand new 1/8" Female NPT in-line air compressor check valve. This check valve features a 1/8" female NPT port in the bottom to go to an unloader valve if needed. This is a universal inline check valve with female NPT threads on each end. This valve prevents back flow or tank pressure from getting back into the air compressor pump once the compressor is shut off. The 1/8" unloader port on the bottom of the valve is used to relieve pressure from the pump once it has shut off, this port comes plugged in case you do not require it in your application. If you need to use this bottom port, simply remove the plug.