Elastoflex S6 is a smooth surface Styrene-Butadiene-Styrene (SBS) modified bitumen roofing membrane reinforced with a polyester mat saturated with a rubberized asphaltic compound. Polyester reinforcement provides superior tear strength and puncture resistance. Elastoflex S6 is designed for use as a base ply or interply layer in multi-layer low-slope assemblies. Membrane is available in a film or sand top surface and a film or sand bottom surface. Application methods include heat welding, when a film bottom surface is selected, and hot asphalt or cold adhesive when the membrane is sand backed. When a top surface film configuration is selected, successive system layers can be heat welded with an additional ply of Elastoflex S6, Elastoflex S6 G or other Polyglass SBS cap sheet. A top film configuration also allows for the application of a variety of Polyglass SBS or APP self-adhered cap sheets.