Cellular PVC wrapped in a rigid PVC shell. Outer shell provides longer life, minimizes damage during installation, and has unsurpassed color and surface consistency. Tongue and groove easy installation, cuts and nails better than wood, and maintenance-free. Water, mold, and mildew-resistant. Ideal for use in wet locations: Bathrooms, laundry rooms, and basements. Color match fill stick available. Flame-retardant (ASTM D635-03). Limited lifetime warranty.