Takes 3 LM8UU bearings.
Comes with an integrated belt tensioning system (see red carriage).
Has integrated slots for cable-ties to get a really firm grip on those bearings.
Fan mount is an option in the scad file if you don't want it.
Works great with one of my extuders mounted at an angle to maximise x travel.
Extruder mounts are intended for M4 screws.
Fan mounts, belt clamps and tension adjustment M3.