I did a lot of research before deciding on these. Love the fact that the bits are attached to a hex shank that fits the drill, but the tapered socket is separate and adjustable. However, I don't like the extra width on the collar body where the set screws are; This can prevent you from drilling the countersink sufficiently deep when using inclined drilling or blind hole methods. Also, the #8 drill bit broke after drilling about 20 holes in a common southern yellow pine. Very disappointing and I couldn't find any replacement bits. Update: I have been able to find bits made by FTG USA that fit the broken #8 bit exactly. Search Revain for "Replacement 3 Piece Core Drill Bits". These bits (and their own full set of countersinks) are virtually identical to Century bits. #8 bits seem to be the only spare size available, but luckily that's the size I use 95% of the time.