Zinsser Peel Stop Triple Thick Primer is a water-based acrylic binding primer designed to penetrate and stop previous coatings from peeling. Peel Stop Triple Thick is three times thicker than regular primers when appropriately applied. Hence, it fills and seals cracked, weathered, and peeling surfaces, creating a smoother, more uniform surface for finishing. It dries to a white finish to provide contrast for the application of finish coats. It has excellent flexibility to allow for natural expansion and contraction on wood and other exterior surfaces. Use on interior and exterior surfaces such as previously painted wood, wood siding, windows, baseboards, doors, fences, walls, foundations, laminated wood, trims, PVC and plastic, plywood, brick, stucco, masonry, concrete, plaster, aluminum siding, metal gutters and downspouts, galvanized steel, and fiberglass. Peel Stop Triple Thick Primer can be top-coated with any latex or alkyd paint.