This is exactly the ring I bought 4 or 5 months ago. Can't remember the price paid but it was around 20$ so I guess it's the same quality...
I did a comparaison of this collar (for my 70-200F4L) and the one of a friend of mine (a canon OEM made for his 70-200 F2.8L) and quality is really good.
The screw is a little less smooth but the main diff is in the lining inside the ring. Mine is made of some kind of velvet and his is a kind of teflon, which is much more soft on the lens.
So if you use it to flip the camera from horizontal to vertical position, you have to take a little more care to avoid scratching your lens' frame.
Overall, highly recommended at that price! I don't regret it. In fact, I also bought from the same seller few days after the ring for the 100mm macro.
Claude