These Z stabilizers reduce the amount of Z wobble by providing additional support to the Z axis smooth rods. Additionally, they are fully compatible with my popular bed stabilizer upgrade found here: http://www.thingiverse.com/thing:43200Works quite well too!Designed and tested for a Printrbot LC, a Printrbot Plus version has also been made to accommodate 12mm rods, though it is untested. Please comment if it works for you!The standard size is .25" thick and the low profile version is slightly thinner at .20". If your printing surface isn't raised by glass or leveling screws, use the low profile version.Volume: .4 cubic inches ABS Weight: .01 poundsPrint two of either the regular or low profile stabilizer. No need to mirror. Remove the X carriage, Z axis smooth rods, and the 2 pairs of screws directly in front & behind the smooth rod hole. Test fit the smooth rod in the center hole of the stabilizer, it should be very snug, if it's too tight, file the inside until it barely slides in. If it's too loose, check your settings or scale down the print by a few percent. Install the stabilizers with the bump pointing towards the center of the Printrbot. You'll need two #6-32 x 3/4" Screws for each stabilizer. Don't tighten the screws all the way until you've reattached the X carriage (for alignment purposes). Notes: Be careful handling your smooth rods! Dropping or mishandling them can cause them to be irreparably bent. The fit should be snug and doable by hand. 2-3 perimeters recommended for strength, low infill is acceptable. For reference when deciding standard or low profile, my print surface is exactly .25" above the LC's wooden bed surface, and this leaves about 1/16" clearance when using the standard stabilizer. I recommend using the z axis stabilizer in conjunction with my print bed stabilizer for additional robustness! http://www.thingiverse.com/thing:43200