RhinoRoof® U20 Underlayment helps seal your home against water damage and other moisture infiltration which can cause mold growth and rotting deck boards. RhinoRooff® U20 is up to12 times stronger than #30 felt and offers excellent wind resistance and durability through heavy roof traffic and adverse weather conditions. RhinoRoof U20 is a highly engineered, mechanically attached, coated woven synthetic roofing underlayment for sloped roofs. The fiber grip textured walking surface can also be chalked just like felt. Unlike traditional asphalt saturated felts, RhinoRoof U20 can be used in extremely low temperatures without becoming stiff and difficult to unroll. It offers superior wind resistance and durability through heavy roof traffic and adverse weather conditions. It lays flat and will remain 100% impervious to mold.