Its the diffuser they put on the 09> cars and it is subtly different from the pre LCI. If you look at the photos at the start of the thread that was the original diffuser and it is smooth and curves round under the car. The LCI has a bit more shape to it and has a lip in the bottom. The photo below is my car with the LCI diffuser. It was about £65 from BMW parts and was simple to change. A decent mod in my opinion.