GTU(TM) Watch Back Case Opener Screw Remover Wrench Tool Kit Set With 12 chucks + Storage Case Condition: 100% Brand New and High Quality Open & close most screw waterproof case back up to 37mm case size Includes four 4 sets of interchangeable chucks: Square, Round, Flat & Knurled Knurled handle prevents losing your grip Chucks are quality made they guarantee not fall off when use