5/16" x 12", Thunderbolt Aircraft Length Black Oxide Drill Bit, Ideal For Extra-Reach, Deep Drilling Applications In Metal, Wood & Plastic, Thunderbolt Web Design Provides Longer Life & Faster Drilling Times, Parabolic Flute, Clears Chips Faster, Black Oxide Construction For Durability, 135 Degree Split Point, Precision Start No Walking.