This spacer is used on the x/y rods of an UMO between the bearing and the pulley. The idea of the design was first introduced by Ultimaker with the UM2.
Technical
1. Print the spacers and cut the caps with a lasercutter.
2. Then remove all 8mm rods and all old caps.
3. Place the new open caps.
4. Place the spacers and the pulleys.
5. Calibrate and your printer is upgraded!