The Polypipe PP6415M 15mm metal pipe stiffener is a high-quality stainless steel insert designed to support and reinforce plastic pipes in push-fit plumbing systems. It ensures joints maintain shape under pressure and temperature changes, preventing leaks and deformation. Compatible with PolyPlumb, PolyFit, and PolyMax fittings, this stiffener delivers long-lasting performance and is ideal for professional plumbing and heating installations.