Harvey Tool 780816-C3 | 1/4" Diameter x 1/4" Shank x 0.3750" LOC x 2-1/2" OAL 4 Flute AlTiN Coated Carbide Square End MillThis 4 flute, square profile offering of Backdraft Cutters is optimized for cleaning up the bottom corner of pockets, and features a backdraft angle to reduce rubbing. Designed to clean up bottom corner of pockets while backdraft angle minimizes rubbing 4 helical flutes (20 Degree helix) Center cutting Solid carbide CNC ground in the USA Product Specifications Cutter Diameter (Inch) 0. 2500" (1 4) Neck Diameter (Inch) 0. 2380" Length of Cut (Inch) 0.