SIPA Synthetic Roofing Underlayment 100 GSM is a lightweight synthetic roof underayment designed to enhance the life of a roof system through superior water resistance and UV protection Coil layer is waterproof layer and anti-aging layer, fluctuation two sides is to enhance blinding layer, firm, and reliable, does not have become warped edge, no empty drum, double waterproof, is a new type of waterproof materials. Benefits of 100 GSM Unique Non-Woven Top Surface Fabric Allows For Enhanced Traction Water Resistant Performance Characteristics Exceed ASTM D4533 & D226