High quality US made tool. 3/8" drive socket replaces every SAE and metric socket from 1/4 in. (0.25) (9mm) to 3/4" (17mm). Automatically adjusts to every size bolt including wire nuts, hooks, square nuts and so much more. Use it with your socket set or with your cordless screw driver with included adapter. Just press it on and turn. It works great with power tools. 54 internal spring loaded roller pins compress and grab anything! High quality alloy steel parts: Copies use cheap soft steel parts that break the first time you use them. Gator-Grip uses hardened alloy steel parts that last a lifetime. Popular Mechanics Tool of The Year!