LeakBarrier® Fast90 Self-Adhering Tile Underlayment consists of a premium quality Organic mat, impregnated with asphalt saturant, then coated with a high-grade weathering asphalt and surfaced with ceramic granules to protect against UV, weathering and physical damage. It has a self-adhering compound on the bottom side and on the side lap, utilizing a highly adhesive SBS modified asphalt protected by a split back release liner for easy installation.