“This is a good design. There is a video online explaining how it works. The smaller end contains a gripper ring that when tightened grips onto a standard blue 25mm MDPE water supply pipe, making sure by inserting the pipe liner. The larger end has an internal seal and spacers that provide a good seal for a specified range of diameters of pipe. In my case it was 25mm and 25mm. The middle is designed well so that when the coupler is fitted, it can be gripped firmly and positioned accurately for tightening at each end.”
