50 -Lb. Bag, Gray, Versabond Flex Fortified Thin Set Mortar, High Performance Formula Provides Outstanding Working Characteristics While The High Flexibility & Bond Strength Delivers Excellent Performance Over A Wide Variety Of Floor & Wall Installations, Exceeds ANSI A118.4 & A118.11, Protected By Moldgard Technology To Resist Mold & Mildew Growth.