Milwaukee's Core Bits are ideal for large hole drilling where depth is relatively shallow. The Core Bit cuts a kerf only. The usable depth of Thick Wall Core Bits is 4-3/8 inch. The inside core must be removed by the operator before deeper drilling can be accomplished. The Thick Wall construction is ideal for larger hammers and more seasoned/cured concrete. A 7-1/2 inch extension is available to allow for the deeper holes to be drilled. The appropriate (dependant on the diameter) Spline Drive Shank must be used to drive the Core Bit. Use 48-20-5199 Center Pin and 48-20-5175 Guide Plate for positioning and starting the hole. Thick Wall Core Bits are available from 1 inch to 6 inch diameters. See Thin Wall Core Bits for less expensive drilling in NEW concrete and/or smaller hammers..SDS-MAX/SPLINE CORE 5" X 4-1/16". The product is easy to use. The product is durable. The product is manufactured in Japan.