The base of the SI-120 has been machined to a flat surface, however it does not have a polished finish. The base is constructed from copper and has a nickel plated finish to prevent it from tarnishing over time. Very fine ridges can be felt by dragging a fingernail across the bottom.
The anti-vibration strips are made of some type of rubbery material that is adhesive-backed. These are installed along the raised edges to help quell any fan noise caused by direct contact with the metal fins.
The clips slip into holes on either end of the fins and are designed to snap onto the lower portion of the fan edge. Most fans have open holes that the tips of the clips would actually sit down in, however even with fans that have solid screw holes, the clips function well enough to hold the fan firmly in place.
Compared to one of its smaller siblings, the SI-120 appears rather large. The primary difference between the SI-120 and this XP-90, aside from their size, is of course the absence of the lower portion of fins.