Let's look at the previous reviews first. This end mill is exactly as described. The coating is titanium aluminum nitride (TiAlN) as described and is actually purplish black in color. This is different from the image, which for some reason only shows titanium nitride (TiN). In fact, TiAlN is the best and generally more expensive coating at higher hardness and temperatures above 800Β°C to create an aluminum oxide layer that reflects heat back into the chip and away from the tool and workpieceβ¦