These white boot covers have serged seams, soles made of polyvinyl chloride and ankle ties made of elastic. These size X-large boot covers have 18 inches of high elastic top and are an excellent barrier for dry particulates, non-hazardous liquids and micro-organisms. They are made from gripper and DuPont Tyvek for durability. These boot covers are Cleanroom Class ISO six (Class 1,000) and above.