Don't bother replacing your OEM fog light lens, it's difficult, time consuming, and will leave your BMW fog lights looking cheap. Most customers of ours want to replace their fogs as over time the light output turns dimmer and the fogs either break, fade, or become overly pitted from rocks and road debris.
We sell the entire assembly, which is a direct replacement for your OEM fog lights. The lenses cost too much, and sometimes are not even available for sale as most BMW fog lights are sealed from the factory. This is important, especially with the later models having plastic coverings, the plastic fades and pits over time, but also remember the heat from the light bulb will cause the 'bowl' of the reflector to depreciate over time, which is where our entire replacement will come in.
The other option of BMW fog lights we sell are the projector style fogs. They are slightly different looking than the OEM counterpart but have a projector beam based output, meaning you can level off and control the light output just like a BMW xenon low beam housing, which are pretty much standard since 2004. If you are going to put a HID or xenon kit in your fogs we highly, highly recommend using the projector based housings, as they are safer for other drivers on the road and will control your light output perfectly.