1. Smooth bore: The drill bit set ensures fast and smooth drilling on various materials, including steel sheets, aluminum sheets, wooden boards, plastic boards, and more. Achieve accurate and efficient results every time. 2. Timesaving design: With 29 different opening sizes ranging from 4mm to 32mm, our cone drill bit eliminates the need for constant bit changes. Save time and effort while effortlessly drilling or enlarging holes of different sizes without interruptions. 3. Comprehensive set with storage box: Your includes three step drill bits (412mm, 420mm, 432mm) and three HSS twist drill bits (3/6/8mm), all neatly organized in a portable plastic box. Keep your tools organized and easily accessible. 4. Wide applications: for sheet metal, sink installation, auto repairs, and more. This step drill bit set is designed to cut through various materials, including boards, aluminum, insulation boards, and PVC panels, giving your projects unmatched versatility.