XSPC Passive Aluminium Reservoir
 

Since this is a passive cooling device it won’t make huge reductions in
the temperature of your watercooling setup. What it will do is keep the
temperatures low even when you lower your radiator fan/noise levels,
allowing you to further silence your system. It’ll look good doing it and
won’t cost a bomb either.

http://www.viperlair.com/reviews/coo.../xspc/passres/