The EVGA Superclock
Figure 4 reveals the front of the heatsink, where the 120 mm fan will be installed.
Figure 5 presents the side of the heatsink. Notice that the fins are folded, creating a closed panel.
Figure 6 shows the back of the heatsink. Due to the shape of the fins and the extended closed surface, the area for airflow exit is smaller than the front intake area.
The top of the heatsink is shown in Figure 7. Note that the fins have a texture in order to create turbulence that improves the heat transfer.