These Forgefix Pipe Collars are made from heat-resistant polypropylene, which is able to withstand the temperature changes in most central heating systems. APPLICATION: Low cost, decorative cover to hide the hole where a pipe passes through a wall, floor or ceiling. 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. It can withstand temperatures of up to 100°C (most pipes in domestic central heating systems operate at around 70°C). Pipe Collar 15mm Box 25