One of these 25mm thick fans out to be enough for even the most die-hard cooling duty. OCZ strap on two of them. The fans are a moderate RPM so noise is minimal. The grills aren't really that necessary, but the positioning of the fan over top of the heatsink is. Rather then the fans' motor being directly above the hottest spot on the heatsink the two sets of fan blades take the spot. The purpose is to move more air down in to this region of the heatsink than would normally be pushed down in typical configurations.

The heatsink component of the twin turbo is a fairly generic extruded aluminum design, which while not originally designed for this configuration has been well adapted.

It has a 7mm thick aluminum base, and oddly 3.75mm deep fin cuts. Looking at the how the clip sits in the clip channel it would appear as though the extrusion has been over-cut by the manufacturer.

The fins have a slight taper to them and go from about 1.25mm to 0.75mm over 29mm for good heat flow.

The over-cutting we spoke of a few seconds ago is a bit more visible in this image. The tapered fins help allow air to move down along each of the fins more effectively.

The Twin Turbo uses a two-part pivoting clip that is easy to wrangle into position. More importantly it doesn't require a screwdriver to remove the heatsink.

We're generally very tough when it comes to the base of heatsink. After all this is the part which makes contact with the processor. The flatter it is the better (less thermal compound required, better surface-to-surface contact, etc.). Extrusions always seem to be among the worst at keeping the base flat, and the Twin Turbo fairs about average. The base is not perfectly flat, but the degree of curve is at subtle. Best to lap this brushed base for a few minutes before installing it on the processor.