2-1/2″ Diameter Diamond Carbide Core Drill. Part of the NEW Ratio Bit System. Cuts hundreds of holes in high strength and HPC concrete. This system works great for confined areas. Also no water is needed when using this concrete coring system. Requires the Starter Pilot Bit. First step is to know what type of rotary hammer you want to use this in. Simply purchase the adapter. EitherSDS-PLUS, SDS-MAX or SPLINE Drive. If you don’t want to bend over, I recommend either a 11″ extension or an 18″ extension. The beautiful thing about this set up is you only need to purchase the adapter, extension and pilot bit one time. Maybe an additional pilot bit but that’s it.