GAF Shingle Mate 36 in x 144 ft 400 sq ft Felt Roof Underlayment Waterproof Flooring heavy duty box trunnion and concave heavy duty box trunnion and concave teeth on the trunnion gears promote easier raising and tilting of saw blade Ft) 5000 Product Width (in 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 Series Name Shingle Mate Coverage Area (Sq