Milwaukee® Thunderbolt® Black compound middleman length drill bits are designed for extreme sturdiness and long life. The Thunderbolt net options a thicker core than a typical drilling bit to produce final strength and shield against side-load breakage. A specially designed parabolic flute kind clears chips quick, whereas the 3-Flat Secure-Grip™ shank holds the bit firmly within the drill chuck. The 135° split purpose tip delivers a exactitude begin and prevents walking for quick, correct holes. Effective for drilling on arced surfaces, urban center Thunderbolt Black compound bits need less effort to drill through metal, wood and PVC, and are extremely counseled to be used with moveable drills.