Connection Fitting M 20x3/4" couplings are ideal for water supply piping aboveground.Couplings pipe fittings are the easiest way to join pipe and do not require soldering, clamps, unions, glue or tools to complete the job. Just insert the pipe and the stainless steel teeth bite down and grip tight, while a specially formulated o-ring compresses to create a perfect seal. Disassembly is just as fast using the simple disconnect tool so fittings and valves can be easily changed and reused.