Firestone SBS Base is a modified bitumen membrane featuring a blend of SBS (Styrene-Butadiene-Styrene) rubber polymer and high quality asphalt reinforced with a strong non-woven fiberglass mat. The addition of SBS rubber polymer optimizes the asphalt blend to increase its natural waterproofing properties, elasticity, adding elongation and flexibility. SBS Base is designed specifically as a base layer for use with Firestone SBS Modified Bitumen Systems, and is ideal for use on both new construction and reroofing projects. The inorganic fiber glass reinforcement resists moisture absorption and provides strength and stability to the product, yielding a membrane that resists natural forces and other factors on the rooftop.