Professional 3-Piece Set: The step drill bit set includes a 13-step bit(1/8-1/2 in) for electronic enclosures, a 9-step bit(1/4-3/4 in) for mechanical assembly, and a 12-step bit (3/16-7/8 in) for mixed ranges, meeting diverse drilling needs Long-Lasting Sharpness: The step bit set is made of cobalt high-speed steel with an AlTiN coating to withstand wear and stay sharp. It is ideal for stainless steel, metal sheets, and other tough materials Optimized Cutting Angle: Our step drill bits feature a 118° tip and four-flute design, ensuring fast chip clearing, less heat buildup, and clean, burr-free holes in wood, plastic, and fiberglass Universal Quick-Change Shank: Hex shank design fits almost all standard drills for quick, secure bit changes