I've got a Bromfication one, which looks identical to some of the Chinese ones (including the Rockbros model) to the point where I suspect they're the same items. Had no problems with it so far.
That's good to know! Is that the one with the built-in seatclamp? Does it have the retaining flange? The pics of the rockbros one seem to indicate it doesn't have one, although the model sans-seatclamp does.
I've got a Bromfication one, which looks identical to some of the Chinese ones (including the Rockbros model) to the point where I suspect they're the same items. Had no problems with it so far.