Bulk Packaged Jacobs 1/2 inch 403-30598 MultiCraft Drill Chuck. Plated body provides a rust-resistant finish. Patented Torx Technology for easy mounting. Through-hardened jaws provide wear-resistant gripping surfaces. Accepts Drill bits from 1/16 (1.5mm) to 1/2 inch (13mm). 3/8-24 Mount. Uses a KK Chuck Key, which is not included.