Perform flexible covering - the perfect replacement for lead Perform is a composite consisting of aluminium mesh, embedded in a special type of polymer rubber. Both of these materials are environmentally sound and UV resistant. The material offers the same functionality of lead, has excellent stretching properties and provides a ‘breathable’ covering which prevents the formation of condensation. Features No scrap value to potential thieves. Lightweight and easy to handle. Great form stability, easily cut and dressed. Use full roll without need for expansion joints.