This type of heatsink has shown up under a couple of different manufacturers names, but so far each version has remained a little bit different than the others. In this case the Evercool ND18-715 is an aluminum extrusion heatsink which has had a thin 3mm thick copper base plate tin-soldered to the base (after nickel plating). The fan and the curve of the fins enable this heatsink to remain pretty competitive amongst thermally while not generating all that much noise.
This is not a silent heatsink, but it is fairly low on the noise levels which is always a welcome aspect. The base of the heatsink is actually smaller than the top which measures 80mm square. In this configuration, and with the help of a small increase in base thickness at the center we have a heatsink which exhausts air with little turbulence or back pressure it seems.