I used this core bit to drill several holes through six inch thick concrete. The pilot bit was too flexible to hold the core bit steady, so I took it off and used a timber starter jig, like what tilers do, to get the core bit started. It only needed the jig for about 5mm penetration, then the core bit stayed straight. I rigged up a garden hose to provide a trickle of water onto the core bit. It drilled at an acceptable rate without much pressure. For the price this core bit was excellent value.