Hellermanntyton straight conduit fittings with swivel external thread hg sm hellermann tyton 166 21304 the hellermanntyton 166 21304 hg28 is a straight conduit fitting with a m25 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 21304 hg28 sm m25 straight conduit