It is frontplate from Aquacomputer Aquadrive that I have put on the original bay covers.
I have 2 of these ones (for my 4 HDD) :
http://shop.aquacomputer.de/images/p...ages/25126.jpg
And I have put only the frontplate on empty 5.25" and on DVD :
http://shop.aquacomputer.de/images/p...ages/93099.jpg
If you want to know more :
Aquacomputer Aquadrive X2
Frontplate for Aquadrive aluminum silver