1/4" stainless steel barb with stainless steel flare fitting nut. The right size for connecting to threaded keg connectors. Leave the barb and nut clamped to the hose. This way you can remove the hose from the ball lock, for cleaning, without cutting hose. Also screws onto our regulator check valves. Fisheye washer is not needed for use with keg connectors but is necessary for any metal to metal connections.