Custom Building Products Gray VersaBond Fortified Thin-Set Mortar, 25 lb. is a polymer-modified Portland cement mortar system designed to provide excellent adhesion to interior surfaces without the need for a latex additive. It is i for adhering 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 types. This mortar also enhances bond strength when used over conventional thin set mortar substrates including concrete, concrete block, wonderboard, gypsum drywall, and existing ceramic tile. Intended for interior use only, it is not for application 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. Model Number: MTSG25