Damp Mop Cover is made of premium, split nylon/polyester blend microfiber that provides optimal damp mopping performance. It slides easily onto Rubbermaid Commercial HYGEN Flexi-Frame (sold separately) that conforms to curved surfaces for better pickup of dirt and debris. Cover is proven to clean floors 45 percent better than string mops and 25 percent better than conventional microfiber. Patent-pending Zig-Zag design packs 17 percent more split microfiber into each mop. Superior construction and premium-grade materials maximize durability and product life. Mop cover is durable through 500 launderings and through 200 launderings with bleach.