It is a smoked tint vinyl overlay. I ordered it off ebay for about $20 shipped. It came with very easy to understand installation instructions. I still need to trim it a little bit, but for $20 I am pleased with the look. PM me if you want me to send you a link to a similar auction or to more pics of it.
2007 E90 328xi Monaco Blue 6MT/COLD/PREM/Nav/Brushed Aluminum/Xenon/Sat Radio
20% Tint/09 NAV Disk Upgrade/Rear Plate PDC/Smoked LED Blacklines/Smoked LED Sidemarkers/WeissLicht LED Halo's/Front LED Signals/Black emblems