Use to tighten or loosen the Chucks. Perfect for most electric drill and power tool. The Ratchets function makes changing the drill bits more efficient Used to adjust how tight or loose the Chucks is, and the drill bits may be changed more quickly thanks to the Ratchets function With a positive and Ratchets switches, it can rotates forward and reverse, and quickly loosen and tighten the drill Chucks, which is simple and Two sizes help you work perfectly. Small head diameter: 12.7mm, big diameter: 17.5mm Adopt carbon steel, wear resistant and has a long service life. The handle is nonslip and comfortable to hold, Manufacturer: XIAOQENAN