The Record Power R150CB Hollow Square Mortice Bits have long windows to allow easy ejection of wood chips, and are readily sharpened at their cutting edge to ensure clean, fast cutting of the mortice. Suitable for use with the full range of Record Power morticers as well as most other machines. Shank Size: 13/16in.Select Option 1/2in1/4in3/8in Add to Basket Quantity