Milwaukee Thunderbolt Cobalt drill bits are designed for extreme durability and long life in specialty applications. The Thunderbolt web features a thicker core than a standard drill bit to provide ultimate strength and protect against side-load breakage. A specially designed parabolic flute form clears chips and debris fast to keep the bit cool. The 135ш split point tip delivers a precision start and prevents walking for fast, accurate holes. Effective for drilling on curved surfaces, Milwaukee Thunderbolt Cobalt bits require less effort to drill through stainless steel, high alloy steel and cast iron. Highly recommended for use with portable drills.