Bi-metal hole saw is compatible with a wide variety of materials like soft metal, wood, PVC board, plastic and drywall. It also cuts faster and smoother and with reduced vibration due to the variable pitched teeth. High speed steel is used on the outer edge due to its wear resistance properties and forms the cutting edge of the teeth. How to Cut Successfully: 1. Install the pilot hole and the hole saw. 2. Holding the drill straight to cutting surface and drill as clockwise rotation. 3. When starting drilling, cutting at a slow speed and holding steady pressure. 4. Then the hole saw cut hole in no time. Warm Tips: 1. Adult use only and always wear appropriate safety gear when using. 2. Due to manual measurement, please allow 1-2mm difference, thanks! 3. Our digital images are as accurate as possible. Because of the difference between the display and the light, the color is slightly different. Customer Service: If you are not satisfied with our hole saw, please contact us immediately. we attach great importance to your feelings and experiences.