They are for use as bearings or high-speed rotating components (no internal clearance spec).
In avionics bays, these spacers secure electronic equipment, isolating sensitive components from the vibrations and G-forces of flight. nas1056 spacers
Tolerances are very tight – typically ±0.002″ on ID and OD, ±0.005″ on length. They are for use as bearings or high-speed