This is a professional 13-PCS drill bit . It includes 5 kinds of hole to meet your professional need: 16mm/18.5mm/20mm/25mm/30mm, each size comes with one piece. Industrial grade high-speed steel for higher durability and sturdiness. Applicable to hand-held electric drill, vertical electric drill and mobile belt drilling machine. Suitable for drilling in tough material, including aluminium, cast iron, brass, copper, magnesium alloy, plastics, etc. for DIY, home and general building/engineering use. Feature - Color: Mainly silver - Material: HSS - Hole drill bits size: 16mm/0.62inch, 18.5mm/0.72inch , 20mm/0.78inch , 25mm/0.98inch , 30mm/1.18inch - High-speed steel with tungsten coating treatment, tougher and more abrasion resistant for longer working life and high work efficiency. - Sawtooth hole designed drill bits, smooth and , high precision, increase drilling speed. - Mainly for drilling wood, plastic, fiberglass, and metal alloy including copper, aluminum, tool steel, cast iron, and heavy-duty abrasive alloy metal, etc. - Applicable to hand-held electric drill, vertical electric drill and mobile belt drilling machine. - 5 sizes of hole to meet your different needs. for DIY, home and general building/engineering use. Package list: 10 x HSS Drill Bit