I have 2 of them they were given out about 2013 at my O local store. I bought 2 50 dollar gift cards and got 2 of them. I still have them like that. I don't think it will actually make a pair unless you were to use some glue..
It said in another post I found after figuring out about it, that it requires sanding of the lenses to get them to fit as well as some other issues with getting them together.