The set contains a variety of sizes, you can freely choose to match, wide application in automobile repairs, household maintenance and most general repairs. High Quality --- The extension adapters are made of chrome steel.Adapters and reducers are made of premium, high-strength chrome steel with a manganese phosphate coating to help resist rust and corrosion and ensure a lifetime of use.Usage General Use --- This screwdriver extension bar set for hex shank screwdriver is designed to meet a variety of needs.Provides versatility and convenience, no matter which tool you choose to use.Purpose ---The spring-loaded ball lock ensures a tight fit in the driver's head to prevent slipping during use.Specially machined to securely fit into a manual screwdriver, drill wrench or impact wrench.