Nylon washer used with 1/4 inch flare fittings. Use the washer anywhere you have metal to metal contact on flare fittings to prevent leaks. This can be on certain types of regulator connections and with stainless steel quick disconnects (like the Torpedo Quick Disconnects)

This gasket is not necessary when connecting female flare fittings to the plastic MFL quick disconnects because they have a plastic washer built in.