perfectly match the diameter of the shank and cutting edge. the coating appears even, which is a good sign. The cut is nice and clean and with a little less noise, so I'm guessing it's the coating. I've treated it with a heat gun during use and found it to run about 1 degree cooler than other uncoated bits. In general I am very happy with it. I would recommend them anytime for hardwoods, non-ferrous metals and acrylic/plastic.