These Thunder Twist SDS-Plus sets comes with multiple bit sizes. Their TriCarb grade tip guarantees linger life with faster penetration due to unceased chiseling action. ThunderTwist flute design combines with a copper brazing alloy creates the mist reliable drill bit on the market. Made with the highest quality American chrome-molybdenum-nickel steel available. Vacuum heat treated, and shot-peened for superior strength under the roughest conditions.