Custom Building Products Gray VersaBond Fortified Thin-Set Mortar, 50 lb. is a polymer-modified Portland cement mortar system designed to deliver excellent adhesion to interior surfaces without needing a latex additive. It is i for adhering a variety of tiles including glazed and unglazed ceramic mosaic, glazed wall tile, quarry, terrazzo, cement-bodied tile, high-lug tiles, and pavers to properly prepared interior surfaces such as exterior grade plywood and many resilient flooring surfaces. This mortar also provides enhanced bond strength when applied over conventional thin set mortar substrates like concrete, concrete block, wonderboard, gypsum drywall, and existing ceramic tile. Intended for interior use only, it is not for use over cushion resilient flooring, hardwood or parquet flooring, particle board, wafer board, masonite, metal, or plastic. Coverage depends on the substrate, tile, and size of the notched trowel, with an average coverage of approximately 2 square feet per pound. Allow the mortar to cure for 24 to 72 hours before grouting, and clean up immediately after use with water. This product is available in a 50 lb. gray bag with a shelf life of 15 months.