Quikrete® Thin Set™ Multi-Purpose (No. 1550) is a blend of portland cement, sand and special polymer additives for the installation of tiles over a variety of surfaces, including properly prepared exterior grade plywood. Requires no additional latex or fortifiers. Quikrete® Thin Set Multi-Purpose is suitable for use as a bond coat for tiles over interior or exterior horizontal or vertical surfaces which are rigid and non-flexing. Available in white or gray.