EsmartD Watch Back Cover Opener Tool Adjustable Wrench Kit With 4 Sets of Champs for Large Waterproof Knurled handle prevents losing your grip Includes four 4 sets of interchangeable chucks: 3 x Square & 3 x Round & 3 x Flat & 3 x Triangle Ideal for large Type Watches.Designed to remove the back lid from watch without marks or scratched Easily adjustable for various case dimensions Metal chucks are quality made they guarantee not fall off when use