Like any high end popular product, fakes will eventually hit the market. The fakes look quite close to the originals in appearance and basic function, but the details of these products fall apart. In the firearms world in particular, the lack of durability and long term reliability are the main drawbacks to knockoffs.
OmahaOutdoors gives some ways to spot fake Trijicon RMRs and Trijicon MROs.
While it can be so tempting to jump on a great deal on a high end product, be careful, it might be a knockoff.
Only buy high end products from reputable sellers.