The Bosch Speed Core system allows a standard SDS rotary hammer drill to drill core holes in concrete in diameters up to 4-3/8". The new Bosch Speed Core system is a simple two piece design. First, choose your SDS core in sizes ranging from 1" to 4-3/8". Secondly, choose from a 13" extension or a 17" extension. The 13" extension will allow you to drill at a depth of approximately 11" and the 17" will do about a 15" depth. The shank includes a built in starter bit, no more loosing the starter pin in the hollow of a wall! This system allows you to have one shank, and several SDS cores. Most SDS rotary hammers will show a rating for core bits. As a rule of thumb, a 7/8" capacity SDS hammer will handle SDS cores around 2-3/4" to 3-1/8" After that you may need a SDS hammer with a 1-1/4" rating. As long as you allow the tool to do the work, you should be OK.