ForgeFix Pipe Clip Double Cliplock - ForgeFix PCDC22, These Forgefix Double Cliplock Pipe Clips are made from heat resistant polypropylene, designed to withstand the temperature changes in central heating systems, and are effective with temperatures of up to 100°C (most pipes in domestic central heating systems operate at around 70°C). Used when fitting most types of pipe work. Polypropylene, also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. An addition polymer made from the monomer propylene, it is rugged and unusually resistant to many chemical solvents, bases and acids. ForgeFix PCDC22 Pipe Clip Double Cliplock 22mm Box 50