A heavy duty, 100% polyester reinforcing mat composed of polyester strands bonded into a random, nonwoven pattern under heat and pressure. An exceptionally tough reinforcing mat for use over existing smooth surface asphalt roofs and some new roof surfaces. Especially designed for use with Heavy Duty and Flex-Shield® Roof Coatings. Embedded between two coats of one of these coatings, it reinforces the coating just as steel reinforces concrete, adding strength, stability and longer life to the waterproofing membrane.