Viking Drill and Tool 6421 0 Type 51-UB Fast Spiral Flute Magnum Super Premium Car Reamer Bit, 5/8" Premium High Speed Steel Car Reamer Fast Spiral 3-Flats on Shank Reamers designed for enlarging previously formed or drilled holes Spiral flute - 3 flats on shank - 1/2-inch shank - gold oxide Minimum starting hole size 7/16-inch Car reamer with stop collar