Philmac Metric/Imperial Elbow is a type of plumbing fitting used to connect two pipes at a 90-degree angle. It has a 20 millimeter metric size connection on one end and a 1/2 inch imperial size connection on the other end. The connection type is Polypropylene Threaded (POL x POL), which means that the fittings have threads that allow them to be screwed into place.