This is a complete X carriage, belt clamps, 608 bearing extruder, PLA linear bearings and all in a single, solid chunk that can be printed out with no support material. This is part of the project to remove Mendel's nuts http://www.thingiverse.com/thing:9005 .OpenSCAD files provided. Note that these files are being messed with and they are currently designed to slip onto two 9.4mm bars set 50mm apart. Should work either way up. The parts list is minimal, but you have to cut grooves in the motor shaft.