13 Piece, Black Oxide Drill Bit Set, Helix Is 31 Degree Which Minimizes The Over Aggressiveness Of A True Parabolic Flute, 135 Degree Split Point For Quick Start & No Walk Applications, Parabolic Flute Design Improves Chip Ejection In Metal & Wood Drilling Applications, Black Oxide Coating For Greater Resistance To Wear, Industrial Grade Steel, For Drilling In Metal, Wood & Plastic, Set Contains Two 1/16", 5/64", Two 3/32", 7/64", Two 1/8", 9/64", 5/32", 3/16", 7/32" & 1/4" Bits.