Armourbond 180 Self-Adhering Base Sheet is constructed of a tough non-woven reinforced polyester mat strengthened with select glass fiber strands that is coated with select SBS polymers and premium asphalt to a thickness of approximately 3.0 mm (118 mils). A thin micro-perforated film covers the top surface of the product, while the self-adhering underside is covered with a removable silicone treated release film. Armourbond 180 provides an excellent base for the application of a heat-welded cap sheet or it may be used when a durable, thick base sheet is needed to adhere to flame-sensitive substrates.