SOPRALENE 180 SP 3.5 is composed of a proprietary formulation of elastomeric styrene-butadiene-styrene (SBS) polymer modified bitumen and is reinforced with a tough and dimensionally stable non-woven polyester mat. SOPRALENE 180 SP (sanded, polyolefin) 3.5 is a SBS-modified bitumen base ply for use in approved multi-ply membrane & flashing assemblies. The topside is surfaced with fine mineral aggregate and underside is surfaced with polyolefin burn-off film to optimize heat welding.