Inline 3/4" Female by 3/4" Female compressed air check valve.  This valve features a side unloader port.  If this is not needed, it can be plugged.  This valve is directional and has the letters IN stamped on the inlet side of the valve.  This valve will keep air from flowing back to the compressor head after the compressor is shut off.  This can also be used in other applications if you have any questions, feel free to contact us at any time.