Their premium synthetic roof underlayment, is among the safest, strongest, and best-performing on the market. It balances strength and weight, provides dynamic steep-slope traction, and will not buckle, warp or crack. FelTex is rated for commercial and residential applications using roofing nails (3/8-inch head), and is an ideal underlayment for asphalt, shingles, metal, tile, slate, and a variety of sloped roofing materials.