You can compare the thickness to an oem lens. Also oem lenses are thinker on one side, so an aftermarket lens would be the same thickness all throughout.So I just picked up a pair of glasses on eBay I know that the frames are real but I am worried the the lenses are not oem is there any way to tell this? They are ruby iridium I can post pictures if anyone would be able to tell from looking at a picture? One other thing that scares me about them is how easy they came out if the frames they came in and into the new frames I will post pics in a little if that will be helpful or if you have any tips I can do hear that would be great thanks