I bought a similar clone in the summer from eBay seller buybuyeasy. It worked fine on the few times I've used it. The cost for mine was lower, at $35 including delivery - for that price, you can't go too far wrong. I generally have it with me if I'm travelling with f/4 zooms and a tripod.
The Canon Tripod Ring Mount A has hinges and the B has the keyed roller fitting. The knockoffs would need to use the same system unless they expect the user to remove the four screws (unlikely).
does depend how much you value your lens and body. These things are cast metal (probably aluminium) and if there is a fault in the casting then you have a week spot which can break. leaving your body and nice lens to come crashing down to the floor.
At least the one the OP mentions is for the 70-200/4 which is not too heavy so should not stress the thing to much. But the 2.8's and bigger lenses could stress it alot more.
Same goes for the knock off wimberly gimbal heads you see.
