This comprehensive 140-piece key kit contains an assortment of square and rectangular keys in various sizes (M3, M4, M5, and M6) perfect for mechanical applications. Made from durable stainless steel, these parallel drive shaft keys are designed for securing pulleys, gears, and other rotating components. The kit comes organized in a sturdy plastic case with divided compartments for easy size selection and storage. These A-type flat keys serve as essential mechanical components for power transmission and shaft-hub connections. The convenient sorting box keeps your workshop organized while providing quick access to the exact size needed for your project. Whether you're working on machinery maintenance, equipment repair, or new mechanical assemblies, this comprehensive key assortment provides the variety needed for most common applications.