Homelux D-LUX Gold, HDURA CI 5US, 54 sq. ft. Crack Suppression and Isolation Underlayment Roll Prevents tile surface cracks caused by substrate movement 100% waterproof (when used in conjunction with joint tape) Fast and easy installation with wide clover leaf holes for optimum mortar contact with tiles Rapid expansion and contraction makes it perfect for use with underfloor heating systems 7/64 in. product height and 1/64 in. foil thickness