AccusizeTools - 1-1/4" Shank to 3/4" Weldon Shank Adaptor for Annular Cutter, IBK0-0258 Weldon adaptor for annular cutter for the 1-1/4" shank to 3/4" Weldon shank Diameter of inner hole: 1-1/4" Diameter of pilot bore: 5/16" Diameter of shank: 3/4"