Henry 444 FRP Panel adhesive 1 gallon pail is a premium, installer-grade adhesive for the installation of fiberglass-reinforced plastic panels. Bonds to concrete, APA grade underlayment plywood (untreated), gypsum drywall and plaster on all grade levels as recommended by the panel manufacturer. Formulated for bonding FRP panels and NRP panels to cured concrete, cement, backer-board, drywall, wood and green-board. 444 FRP Adhesive will cover 90 sq. ft./gallon. with a 1/4 in. trowel. High strength construction adhesive for FRP Panels. The FRP adhesive has a high strength while being fast setting. moisture resistant, and nonflammable. No open time required, 30-minute working time. Henry's Best 10 Year warranty back this high-quality product.