Set of 13 premium cobalt Tri-Bore drill bits made with M35 steel containing 5% cobalt for superior strength and heat resistance. Their third cutting edge increases the cutting surface area allowing for 17% faster cutting while reducing heat buildup and wear to improve service life up to three times longer than standard cobalt drill bits. The third cutting edge starts on drill bits with 1/8 in (3.17 mm) diameter and larger. MIBRO Tri-Bore cobalt drill bits fully ground manufacturing ensures straighter, more precise holes. A thicker core increases the drill bits' rigidity and strength. These drill bits are suitable for the heaviest and most demanding user for drilling in all ferrous and nonferrous metals, including hard steels like stainless steel. For a sure grip, all sizes 3/16 in (4.76 mm) in diameter and larger have three flats on the bit's shank. Their 135° split-point tip geometry on all bits 1/8 in (3.17 mm) in diameter and larger eliminates the need for a center punch and keeps the drill from "walking" on hard surfaces.