It’s only the voltage of 12 V to install at any place of R8 light system. Any car should have brake light working and Audi R8 isn’t an exception. Popular base W2.1X9.5D was used in this system, but power should be at 16 W. For engine volume 4.2 cars normal long lasting bulbs of Audi were installed. It all provides normal work of Audi R8 4.2 electrical system.
Be careful at buying any other lamp for R8 4.2 than recommended by Audi. When purchasing light bulbs for 2011 year vehicle don’t take other base than W2.1X9.5D and look at voltage – it has to be 12 V. Electrical module of 2009 Audi R8 may be destroyed with other lamp characteristics.