The bit has 2 grooves. One looked normal, the other was obviously defective. Instead of a flat piece of carbide that was sharpened to the cutting edge, the carbide was curved, resulting in the center of the cutting edge. In fact, it was made weak. How could it pass any reasonable quality check? So basically I got a single edge cutter with a counterweight on the other side. Since I was milling plastic, I got by with this, but there was a lot of chatter when cutting. I think you get what you pay for. For $11 I did some basic work, but I don't think I'll ever be able to use this bit for a real woodworking project. 3% of reviews mention such poor quality - you had to believe them.