Use this Vapor Check Valve to return vapor to the truck during terminal loading and service station drops. The 3" poppet opens when coupled and closes when disconnected, preventing the vapors from escaping into the atmosphere. The valve has 3" or 4" female NPSM threads, a 4" cam and groove, and tapped mounting holes for the EBW Air Interlock Brake. The 303 series is available without a poppet to serve as a male quick coupler with an Air Interlock Valve mounting pad.