This bur is Tungsten Carbide and 2.3mm in diameter. This is a finishing carbide; cuts and finishes on wood at the same time. No other bur is necessary for a smooth finish. We sent this bur and it's smaller version the 7404 Carbide to a few of our customers for a product review before we started selling them and received AMAZING feedback on these burs. One response was; this "bit(7404) CUT LIKE BUTTER! It also left an incredibly smooth finish, I will have to do no more to the finish. I love it. I highly recommend this bit, and next time I order, I will be getting another to keep on hand. Thanks again. - Judy"