ELGEF Plus electrofusion couplers are grouped into various size ranges. In this way, individual dimension requirements are fully satisfied. In the smaller sizes a coupler is available which especially fulfils service line conditions. Couplers up do d63mm can be easily matched with all GF Piping Systems threaded transition adapters. The active reinforcement used for large couplers compensates for large differences in outer diameter tolerances. The extra large clearance permits easy assembly and accomodates the pipe ovality often found in practice.