I have used these in the past. In regular cinderblock they work nice and in medium concrete. In hard baked glazed brick and very hard concrete, a high speed will put them in; but pressure is needed to keep the bit from riding up. If powered in on too low a speed the screw binds and the bit will ride up. The screw should be removed and put a new screw in. The second time in with a new screw or not will not be near as tight or hold near as good as the first time. Bottom line is make sure you have a drill-driver that will do it the first time. Also make sure your bits are in good shape and keep plenty of spares, and best of all use standard hex driver bits if possible. ............bob
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