E5610CA000 - BRZ REAR UNDER DIFFUSER GENUINE
 

Here is the install guide for under diffuser OEM.
As I installed last year a clone one (pu black matte) bought on eBay for about 90$, I see now installing the genuine one (after a back crash, insurance pays me for the genuine :) ) that items are equivalent.
Same fitting, same bolts and clips.
There are some differences in quality about paint and internal structure but are almost the same (clone and genuine).
So here : https://dl.dropboxusercontent.com/u/...UINE%20OEM.pdf