This 5 mm thick padded cotton cover is intended to protect your HealthyLine mat from sweat and dirt, protect your skin from hot stones, and to make the mat surface more comfortable. Fit mats sized at 18" x 18", 20" x 20", 32" x 20", 36" x 18", 40" x 18", 40" x 20", 40" x 24", 42" x 24", 50" x 24", 52" x 28", 60" x 24", 72" x 24", 72" x 32",  74" x 28", 76" x 32", 80" x 40", 80" x 54", 80" x 60", 80" x 76". The top is made with 100% cotton, while the bottom is medical-grade polyester that is 100% waterproof. These materials do not block negative ions and far-infrared.