This is parametric using the simple equations found in the Solidworks 2014 source, but the wall thickness is static at 1.5mm thick. . The size of your nozzle will determine how many teeth you can print with a 0.5mm nozzle being able to do 18 or possibly 19 teeth before there are no gaps between them. For a 0.35mm nozzle you should be able to do 20 or 21 (depending on how well your printer is calibrated) before the same happens AND both of those are based on the 8.1mm inside diameter LM8UU version. . I added a 16 tooth version for people who might have issues with the 21 and/or 18 tooth versions.From his instructions (rewritten for clarity) - First thing ... simply insert the printed bearings on your rods, and "play with them" by rolling/sliding them up and down to ensure they slide well just remember you SHOULD lubricant them as the lubricant will stay between the teeth. . Simply print slow with 0 infill and (int((1.5/nozzle size)+0.5)) vertical shells and 5 top and bottom horizontal shells. . . Personally I used 20% infill as 0% was a tad weird in Slic3r but in Simplify3d it was beautiful so your slicer will affect this.