This is a heavy duty set of hole saws for cutting sheet metal such as metal. B. Electrical boxes. Despite the high price, the quality of the kit does it justice, from the box to the drills and cutters. Although the drills are "split-point pilot drills for faster penetration and less travel," I still used care and pressure to keep the drill from wandering. to keep the drill from entering the inside of the box. Three drills have plug ejector springs tightly wrapped around them, but when I unscrewed the drill once without loosening or removing the drill, the spring shifted and stayed in the center hole of the cutter. It took a little effort to get the spring out of the hole and back to where it should be on the drill. It's okay, but don't repeat my mistake. Instructions going as far as recommending rotation speeds for different hole sizes. There is nothing that can help a beginner in assembling the drill, chuck and cutter. Rocket science, but the product and some of its users would benefit from more build detail. All in all a good set made in USA that will last for many years.