Hellermanntyton straight conduit fittings with swivel external thread hg sm hellermann tyton 166 21303 the hellermanntyton 166 21303 hg21 is a straight conduit fitting with a m20 swivel external thread and belongs to the hg sm series the body of this one piece conduit fitting has been manufactured from polyamide 66 pa66 with the screw thread fitting produced from nickel plated brass npb it is highly resistant to solvents and oils hellermanntyton 166 21303 hg21 sm m20 straight conduit