Advantages of our Bi-Metal Hole Saws Most users prefer a bi-metal hole saw for the majority of their work because it is compatible with a wide variety of materials. It also cuts faster and smoother and with reduced vibration due to the variable pitched teeth. Hole saws have two different types of steel joined together to form the edge of the cutting end of the hole saw. High speed steel is joined to a soft spring steel to form a durable edge that will cut a multitude of materials and help provide long life. High speed steel is used on the outer edge due to its wear resistance properties and forms the cutting edge of the teeth. Soft, spring steel creates a flexible backing material that allows the hole saw to absorb impacts of the job of drilling holes in difficult-to-cut materials. A good bi-metal hole saw will easily cut through softer materials, such as plastic and wood-based items, as well as harder materials, such as steel and stainless steel. The type of high speed steel chosen by the hole saw manufacturer will contribute greatly to the performance of the hole saw. The best bi-metal hole saws will be made with high speed steel that has a high percentage of cobalt content. We use only high quality high speed tool steel in the manufacture of our bi-metal hole saws. This material contains approximately 8% cobalt to help maintain tooth hardness at high operating temperatures, which helps to maintain the teeth's sharpness of the cutting edge. Package Included 1 x Bimetal Hole Saw 1 x Simple Hole Saw Arbor