This is a simple bending spring foot that dampens the conducted vibrations from your printer to whatever surface it's standing on. These feet clip onto any M8 threaded or smooth rod. It is extremely effective at decoupling low frequency noise from a surface. The feet have holes for permanent mounting on a surface. Also, as my printer is pretty heavy, these feet are very strong and will easily support a heavy prusa i3 with filament reel on top. The clips are very snug and secure.
In order to dampen higher frequency noise as well, add a little bit of PU insulation material (foam) under the foot as shown in the application image.
The combination of 4 of these feet and the insulation material made that I cannot hear the printer anymore behind a door. Airborne noise is already blocked pretty well by the door, but without the feet, the table it's standing on as well as my floor acted like a sound board. Other spring feet, like vector's feet (http://www.thingiverse.com/thing:21855) didn't fit my printer.
The model is designed in CATIA, CATPart file can be downloaded and modified if you wish.
Printing tips: I printed mine with PLA, 0.35mm nozzle, 0.25mm layer height, hexagonal fill 40% on Marlin firmware. Firmware with curve look-ahead (like Marlin) is highly recommended, as the feet derive much of their strength and flexibility from the continuous curve of the perimeters.