Style 39 Insulating Couplings are widely used on gas service lines to be electrically isolated for cathodic protection, or for insulating between pipes of dissimilar metals The Style 39 coupling follows the same basic design as the Style 38 coupling, but has insulating properties. The insulating gasket has a skirt, which extends under the follower ring to insulate it from the pipe. In addition, a “full boot” plastic tubular insulator inside the middle ring assures isolation of pipe ends. Thus, one pipe end is completely insulated from the coupling and opposite pipe end, while the armored gasket on the other end bonds the coupling to the pipe where it can share cathodic protection currents.