Specifications: Material: Alloy. Size: 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm(Optional). Quantiy: 1pcs. Features: The alloy cutter head is made of alloy blade, which is combined with the inner, middle and outer three blades and the front and rear inclination angle design. Center positioning, precise hole drilling, accompany center positioning drilling, positioning before drilling, equipped with a discharge spring to ensure accurate, fast and stable cutting of holes. Universal triangle handle, effectively prevent slipping when working, suitable for 10mm and above chuck. Usage Notice: 1. This hole opener with positioning center drill needs to be manually installed and tightened. 2. During the hole drilling operation, the center drill is positioned to cut first, and the cutter head does not start operation until it is in place. The center drill plays a positioning role. 3. For continuous cutting, please select a lower speed. 4. In order to prevent chipping, please don't let the edge of the hole cutter not be violently hit by the cutting material instantaneously. 5. Need to add water or coolant to reduce the temperature, otherwise there is a risk of burning out the drill bit. 6. The operator should wear protective glasses to protect the glasses. When the face is up, you need to wear protective masks. 7. Keep earplugs in place for long-term operations to reduce the impact of noise. 8. After a long period of operation, the hole opener is in a hot state, so you should pay attention to avoid burning your skin when replacing it. 9. After use, apply anti-rust oil, the service life is longer. Package Included: 1 x Alloy Hole Opener(Optional). 1 x Wrench