describeSTRONG:Sies colches made of HSS (High Speed Steel) M35 are heat resistant, wear resistant, high toughness, high hardness up to 63 - 65 HRC.Sharpness:The cutting blade is professionally heat-treated and thermally cut, finely ground and shaped, ideal for fast and precise cutting of thin materials. Suitable for stainless steel, copper or aluminum sheet, plastic sheet, etc.Low Impact:The concept of spring provides a buffering effect during high-speed drilling, preventing excessive pressure from being applied. Perfect for use on portable drills, bench drills, drill presses, and more.Note:The object to be cut should be fixed, and the drill bit should be perpendicular to its plane. TIP: Add coolant to the edges of the holes to avoid overheating, and wear eye-protection goggles.Tallie:Suitable for hole size 16mm/0.62'', 18mm/0.71'', 20mm/0.78'', 25mm/0.98'', 30mm/1.18''Quantity: 5 pieces