Bosch Quick-Change Extension for Self-Cut Drill BitsBosch Quick Change Extension for Self Cut Drill Bits 1 4" Hex Shank Extension 305mm for Self Cut Speed spade bits delivers extended reach when drilling. This extension is ideal for all applications with spade bits where extra length is needed. Bit has a 1 4" hex shank, intended for use with drill drivers. (2608587520) Specifications Accessory Fitting: Hex Shank: Size1 4" Accessory Fitting Style: Hex Bit Type: Holder Extension Product Length: 305mm