This keyless chuck handles drill shanks up to 1/2". It has a Jacobs 33 taper and comes with an arbor with Jacobs 33 and 3/4 straight shank. This is an excellent choice for those using our power drawbar and the ST-165 set of ER 20 collet chucks. The drill chuck can also be used with your standard R-8 mill arbor or the Morse # 3 tailstock arbor.