SOPRALENE Flam 250 FR is composed of a proprietary formulation of elastomeric styrene-butadiene-styrene (SBS) polymer modified bitumen and is reinforced with a tough, dimensionally stable non-woven polyester mat. The topside is surfaced with ceramic coated granules and underside is surfaced with polyolefin burn-off film to optimize heat welding. SOPRALENE Flam 250 FR GR (fire retardant, granulated) is a SBS-modified bitumen cap ply for use in approved multi-ply membrane and flashing assemblies.