Milwaukee 6-Inch Thick Wall Core Bit is designed for large hole drilling where the depth is relatively shallow. This core bit cuts a kerf only, with a usable depth of 4-3/8 inches. Operators need to remove the inside core before drilling deeper. Its thick wall construction makes it i for use with larger hammers and more seasoned or cured concrete. For deeper holes, a 7-1/2 inch extension is available. The core bit requires the appropriate spline drive shank depending on the diameter to operate effectively. For positioning and starting the hole, use the 48-20-5199 center pin and 48-20-5174 guide plate. Thick wall core bits come in diameters ranging from 1 inch to 6 inches. For less expensive drilling in new concrete or with smaller hammers, consider thin wall core bits. Model Number: 48-20-5165