The Dresser Style 850 Insulating Sleeve is extensively used by gas utilities to simplify the application of cathodic protection to existing steel mains. The Style 850 is used with a conventional tapping machine equipped with a shell cutter or a hole saw to completely sever the main inside the sleeve.  One end of the 850 is effectively insulated from the main by means of high dielectric insulators, while the other end is conductive, tying the sleeve into the existing section of the main under cathodic protection.