Features:High-accuracy thread and tapered holes can be tightly attached to the tool. The housing is treated with electrophoretic paint, making the product anti-rust even in worst environment. By using anti-thrust bearing to convert key-applied torsion into superior gripping. The clamping jaws are specially treated to improve wear resistance. 3-16mm 1/2-20UNF: 3-16mm denotes that clamp the drill between 3mm and 16mm, and 1/2-20UNF represents a screw hole with 1/2-20UNF at the back of the chuck. Specification: Clamping range: 3-16mm / 0.12-0.63inPackage List:1 x Drill Chuck1 x Key1 x 1/4 Hex Head Adapter.Note:Please note that the new type and old type of this product will be sent randomly, and make sure you will not mind before ordering.