An extremely flexible torch-applied SBS membrane. Fastorch SBS is superior to APP membranes because the asphalt is modified with Styrene Butadiene Styrene (SBS) a synthetic rubber, providing it with a rubberized property. APP membranes are manufactured by blending the asphalt with Atactic Polypropylene (APP), which is basically asphalt that has been modified with plastic. The addition of SBS to rubber makes the membrane easier to apply than other products, with better adhesion to metal and end laps.