This adapter is convenient when the diameter of your shift knob changes, such as when switching vehicles. If the diameter and thread pitch of your car's shift knob lever are 8 x 1.25mm, you can install a shift knob with a size of 12 x 1.25mm. (However, the lever will be about 2mm longer.) Material: Aluminum alloy Total length: 14-15mm Shipping will be by non-standard mail, but shipping is free.