These are awesome, high quality, custom made aluminum spacers. They are great at making sturdy standoffs/spacings for your projects.
Metric version of the spacer is 10mm OD which makes a very stable platform.
The spacer has M5 ID to give a thicker wall to keep the screw snug and centered.
These spacers can be used in all sorts of builds. For example, We use the spacers to create a space between the stepper motor and motor mounting plate. This allows for room to mount hardware such as couplers and belt pulleys to the motor shaft.