Solid: Colches made of HSSHigh speed steelM35 refractory, wear-resistant, high toughness, high hardness up to 63 - 65 HRC. Sharp edge: Cutting blades through professional heat treatment and hot cutting, fine grinding forming perfect for quickly cutting thin materials accurately. Suitable for stainless steel, thin copper or aluminum plate, plastic sheet etc. Low impact: The spring idea provides a buffer effect in the high-speed drilling process to prevent putting too much pressure. Very suitable for use on portable electric drill, bench drill, drill press etc. Attention: The cut object should be fixed well, and the drill bit should set perpendicular to its plan. Tip: Add coolant to the edge of the hole to avoid overheating and wear the glasses which can protect your eyes. Tallie: For holes of 16mm/0.62'', 18.5mm/0.73'', 20mm/0.78'', 25mm/0.98'', 30mm/1.18'' Product material: high speed steel Product packaging: a hole opener and a hex wrench in a transparent plastic tube, 5 plastic tubes in a bubble bag Function of product: cooperate with power tools, such as bench drills, to open holes in metal plates such as iron plates and aluminum plates. Size: as shown< /p> Color: silver Delivery quantity: 5pcs/set.