BlueSpot 3PCE 1/2" Alloy Wheel Impact Sockets The BlueSpot 3PCE 1/2" Alloy Wheel Impact Sockets are manufactured from chrome vanadium steel. The sockets are designed for use with alloy wheels that have a 17, 19 or 21mm nut. The sockets feature a protective nylon sleeve around the thin wall to avoid damage to the alloy wheel. The sockets are also colour coded so you can quickly and efficiently choose the correct socket for the wheel you are working on. To activate the manufacturers lifetime guarantee, you will need to register the product on the Bluespot website within 30 days of purchase.