This larger capacity chuck for the UJK drill guide is able to take drill bits with shanks up to 13mm diameter. It is industrial quality with fully hardened and ground working components, offering high accuracy, grip and durability. The chuck has an internal Jacobs Taper (JT2) that will press-fit onto the corresponding JT2 arbor on the drill guide. The Jacobs taper is self-locking and ensures concentricity. When fitting, carefully degrease and clean the arbor and taper before fitting.-bg