DIN 3902 Series is a common male with three different possible female halves. The straight metric thread male has a 24° angle. Its recessed counter-bore matches the tube O.D. it is connected to. The female may be one of the following: A tube, nut and ferrule (compression style), a tapered nose flareless swivel, a tapered nose flareless swivel with a DKO style O-ring in the nose.