This is a Single Bearing Delrin V Wheel by Bart Dring http://www.thingiverse.com/bdring from http://store.makerslide.com/ .There are also copies of this single bearing V wheel, in various formats, included in files on the MakerSlide Extrusion page. http://www.thingiverse.com/thing:8992MakerSlide is an open source motion control hardware system based around aluminum extrusion with integrated V-rails. It makes designing light-duty CNC systems easier and more affordable. http://www.makerslide.com/Use this along with the MakerSlide V-rail extrusion model: http://www.thingiverse.com/thing:8992 and end plates: http://www.thingiverse.com/thing:12507 http://www.thingiverse.com/thing:12504 to design your own motion control systems in OpenSCAD.