Watch Case Opener Adjustable Screw Back Remover Waterproof Wrench Repair Tool This High Quality toll is designed to open and close screw back watch cases. Will open Large majority of watch backs that are screw fitting Made from High Quality Stainless Steel. Comes in a Hard plastic Storage box 18 Tips if 6 different sets. Knurled handle for firm grip Adjustable Thumb Wheel. Maximum Jaw opening 35mm. Works with Round, Square, Hexagonal and serrated backs