GAF Shingle Mate 36 in x 144 ft 400 sq ft Felt Roof Underlayment Waterproof Flooring trailers and more trailers and more Pick set: up to 50% more durable with all metal core ) 36 Width (Inches) 36 Length (Feet) 144 Warranty Limited lifetime Ice and Waterproofer No CA Residents: Prop 65 Warning(s) No UNSPSC 30151500 Material Felt Helps prevent wind driven rain (or water from other sources) from infiltrating under your shingles and causing damage to your roof structure or the inside of your home Looks better: fiberglass reinforcement helps resist wrinkling buckling and lies flat under shingles Eliminates the need to slit bubbled felt (which can compromise the waterproof integrity of your roofing system) Lighter and easier to handle than #30 felt