Open That Milk Line: The actual flow opening on a flapper valve is about 3/4": Half the size of the standard 1.5" milk line. A dairyman spends thousands of dollars on a receiver, inserts a rubber flapper valve and cuts the volume in half, thereby reducing the receiver's efficiency. Replacing the rubber flapper valve with a stainless steel ball check valve opens the line to its full capacity: nearly a 70% performance increase.Positive Shut Off: Ball seats in shut off creating a positive seal. Standard Fittings: Fits standard Tri-clamp fittings.