The ULTIMAT mats are filled with 1-3/8" cross-linked polyethylene and folds in 2' sections for ease in handling and storage. It's upholstered with a tough 18 oz. vinyl fabric. Knife-coated on both sides, the 5.3 oz. polyester base fabric provides excellent tensile strength that resists abrasions, tears and punctures. It is also treated to resist fungus, bacteria and mildew as well as provide years of hard use.