For Milwaukee 14 in. x 4 in. High Speed Steel Pilot Bit, 12 pack Model Number 49-56-8031 Thunderbolt pilot bits are designed for extreme durability and long life. The Thunderbolt web features a thicker core than a standard pilot bit, which provides ultimate strength and protects against side-load breakage. A specially designed parabolic flute form clears chips and debris fast to keep the bit cool. A precision start, 135 split point tip starts on contact to keep the bit from walking for fast, accurate holes. Excellent for drilling on curved surfaces, requires less effort to drill and is highly recommended for use with portable drills.