These white boot covers have serged seams, soles made of polyvinyl chloride and ankle ties made of elastic. These size medium 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.