[High-quality materials, quality assurance] The drill bit holders and cone drill bits are made of high-quality HSS stainless steel, durable. Operation suggestion: When using the electric drill, it should be as vertical as possible, do not shake or tilt, and the electric drill should not rotate too fast. 【Time and labor saving, efficient and fast] The HSS cone drill bit is made of high-speed steel, which can reduce heat and friction, cool quickly, and automatically remove debris in the hole when drilling. The spiral design can prevent slippage, making drilling easier and more efficient. 【Three sizes to meet your needs】4mm-12mm, 4mm-20mm, 4mm-32mm, you can choose different drill bits according to your needs. 【Wide range of uses] The product can process thin iron plates, aluminum, insulation boards, PVC boards, wood boards and other materials with a thickness of up to 4 mm.