Double ended drill bits have twice the drilling life of normal drill bits and is perfect for machinists, stationary drills, and production work Extra strong, heat resistant M35 cobalt high speed steel does not wear out fast providing long service life High speed 135° split-point tips not only penetrate through sheet metal faster, but last six times longer, self-center and provide a true start Double sided drill bit has a versatile design to work with carbon steels, alloys, sheet metal, wood, plastic, PVC, drywall, composition board, and more