Zalman CNPS9900 NT
CNPS9900 NT is amazing. From a front view (Figure 3) it looks like CNPS9700 NT, which also has the round-shaped heatsink with heatpipes inside the fins, made of nickel-plated copper, giving both durability and a nice dark looks.
In a side view, however, the difference between those two coolers is clear: on the other model there is only one heatsink, while on the CNPS9900 family there are two independent heatsinks, one in front and another behind the fan.
The front heatsink has only one heatpipe (with both tips connected to the base from the cooler), but the rear heatsink (shown in Figure 5) has two heatpipes. This, and the fact this heatsink is bigger and receives the direct airflow from the fan, made this heatsink responsible for the most of the heat exchange, and we can say that the front heatsink is an auxiliary one.