They hold the mdf frame together if yours has loosened up like mine hasThey cut the noise of the machine down by well over 50% if you have your printer on a surface that likes to resonate sound.It helps keep the printer in one place when it starts moving really fast, before mine would tend to walk around my desk. You can also apply adhesive tape to the feet more easily to help keep it in place.I recommend printing these at a 15-20% infill with 2 shells and 2-3 top and bottom layers. Don't do much more infill because it will mess with the sound absorbing properties. Obviously, print at least 2, although theoretically you could have as many as you wanted! They take about 8-10 cubic centimeters of material for each strut.