Milwaukee® 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, 135º 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