The XeroSox is Completely Watertight Keeping your Bandages, Prosthesis, and Casts Dry. The XeroSox Pro Pump offers the only leg and arm cast protection in the world with the patented vacuum seal to keep your bandage or cast dry. It is so completely and totally waterproof, between the waterproof fabric and the vacuum seal, that you can even dive off a diving board or ride the ocean waves and still have your cast stay completely dry. Large Half Leg, Length 23 1/2 inches, Opening 11 inches