Firestone BASEGARD SA Base Sheet consists of a Styrene-Butadiene-Styrene rubber modified and self adhesive asphalt blend reinforced with a glass fiber mat and coated with a fine mineral release agent on the top surface and an opaque release film on the bottom surface. This sheet can be used as a base layer or as an effective vapor retarder. When used as a vapor retarder, ISO 95+ GL Insulation, RESISTA™ Insulation or ISOGARD HD Cover Board may be adhered to the top of BASEGARD SA Base Sheet with I.S.O. Twin Pack Insulation Adhesive, I.S.O. Stick Insulation Adhesive, I.S.O. Spray R Insulation Adhesive, or hot asphalt.