Amana Tool 45950 Core Box 2-Flute Carbide Tipped Router Bit with Ball Bearing Guide, 1/4-Inch Shank Cutting diameter 1/2-Inch, 3/8-Inch cutting height 1/4-Inch radius Shank mounted ball bearing guide. 1/4-Inch shank, 2 flute Carbide tipped, industrial quality