Ball bearing module

Ball bearing module, replacement for short adafruit-like linear baring modules. Distance between mounting holes are 18mm and 24mm.
Supposed to be used with 8x3x4 ball bearings, like MR84-2RS.
Thread must be manually cut in the module to allow 4mm blots to be screwed in.

Modified carriage http://www.thingiverse.com/thing:451373