If you search through the old forum posts there are several threads that compare and contrast aftermarket lenses vs OEM. I think I can basically summarize them by saying the optical quality varies widely between aftermarket lens manufacturers with linegear being the most preferred next to OEM or a correctly chopped OEM lens. A general consensus is that you should buy OEM if possible or have a lens custom cut (chopped) for you from a suitable Oakley OEM donor lens. If you want to read more about the optical quality/the rigorous impact testing Oakley lenses undergo you can find that info on Oakley's website (the impact testing is pretty cool- Oakley wants to keep your eyes safe!)