Compression Reducing Coupler MDPE pipe couplings are used to join two lengths of MDPE pipe together. These reducing couplings allow pipes with different diameters to be joined. These pipe couplings are simple to install and provide a strong compression fitting joint. To maintain a rigid and reliable joint connection, it is highly advised that pipe liners (also known as stiffeners or inserts) are also used . Material: polypropylene Compression fitting Available in sizes from 20mm x 16mm to 110mm x 90mm