It's far from a knock off. I would say it's a better designed version of what many other shops sell.
I say this for two reasons:
1) It's is solid aluminium and very sturdy. It does not flex like many of the other solutions on the market;
2) It has 2 additional mounting holes that the other solutions on the market do not have. This ensures the optibay does not move while it is in your computer, and you do not need alternative solutions to secure the bay when it is inside your machine.