Belt tensioner

A simple, no fuss, do-its-job belt tensioner for 6 mm width belt (GT2).
2 measures are available and any other combination of thereof:
- 2 mm
- 3 mm
- 4 mm (2+2)
- 5 mm (3+2)
- 6 mm (3+3)
More than this, you probably need to address it another way...

For convenience, the value by which the belt is shorten is written on the back.
Used on a Kossel Delta.