When installing your Power Tank regulator onto your tank valve you will notice that the flat end surface of the valve mates up to a flat surface inside the regulator attachment nut. Between these surfaces lies a flat seal which stays with the nut, hence the name "never lose". This seal will age and crack over time (usually years) and will leak. Do not over tighten this nut. The torque spec is 10-20 ft./lb. (two finger). If you over tighten you will over squish the seal and cause it to crack sooner than later.