This tee uses compression joints to bring together two runs of MDPE pipe. Made from tough and long-lasting polypropylene, our MDPE fittings utilise an acetal grip ring and a Nitrile rubber O ring.Pipe liners (or stiffeners as they are sometimes called) should always be used with this type of fitting.This fitting is WRAS approved. All of our MDPE fittings can be used on either blue (potable) MDPE pipe or black (non-potable) MDPE pipe.