Description: FunctionProfessional watch maintenance tools for watch back case open requirements, opening and closing screw back case, making it an essential addition to any watch repair kitQuality MaterialWatch Back Case Opener is made of quality steel, high hardness, good toughness, high strength ensures durability and reliable performanceGrooved Chucks SizeIncluding Handle and 7 Grooved chucks(30.5/31.5/32.5/33.5/34.5/35.5/36.5mm),Suitable for 5539 and other watchesWatch Repair ToolGreat for opening and closing waterproof watch back case to provide flexibility and precision in your repair tasks, Necessary tools for watchmakers and watch repairing workersEnthusiasts and Experts: Whether you're a professional watchmaker or an enthusiast looking to perform your own repairs at home, this tool offers the precision and quality needed for effective maintenance work Specification: Material: Steel Package Includes: 1 Handle7 Grooved Chucks Note: Please allow slightly errors due to manual measurement and different monitors.