CONBEE 18mm to 60mm New Watch Repair Tool Back Opener Large XL Wrench Waterproof Screw Case (Silver) Easily adjustable for various case dimensions 18mm to 55mm Key for waterproof watch-cases, with 4 sets of clamps (round, flat, square, triangle) Clamps includes: 3 x Flat, 3 x Square, 3 x Triangle, 9 x Round 3 adjustable jaws