This is designed to slide fit into a T slot, and have a small rubber damper directly fastened. Using only four units at each corner, this design comfortably supports my 35 lb./15 kg Scalar printer I built, off of this design platform; http://www.thingiverse.com/thing:891409
Here is my build;
This part is designed to be a high tolerance press fit into the T slot to avoid creating any noise, and to ensure the vibrations are transferred into the rubber damper.
For each unit, you will require a 6-7mm M3 fastener, a single M3 nut, and a rubber foot designed for an M3 sunk fastener.
Again, these parts are a very snug fit in the T channel, and are held in position by this snugness, NOT by the M3 fastener!
Your mileage may vary with your printer, you may need to scale to 98-99%, no lower, to get these to fit into your T slots, depending on the extrusions you have and the material you choose to use. (Recommend PLA) Having tight printing tolerances matters with this part.
Not tested at a lower(numerically higher) print resolution than posted.