It's metal and you can store it, if you don't need it, in the rear center console ("IN" the rear center consoles cupholder).
No cupholder, just the place to put it, in this pics:




Under the lid in the rear center console there is the second cupholder, and this is where you store the one for the front (you can use the rear without installing the front too!):


Here you can see the front cup holder:

 

why would they put wood surrounding the drivers vent??? BMW is doing a bad job trying to save a few bucks on the wrong places

 

nice