This is a printer-scaleable, hand-operated Nut Driver.
Plastic, so it won't generally scratch things like pliers do... but it is not an heirloom tool you can pass-down to your grandchildren. Plastic is generally good for ~10 hand-tight installations and removals, or dozens of snug-tight cinches.
The .stl size is 10mm, so if you need a different size, just scale it.
A 12mm driver would be 120%.
A 6 mm driver would be 60%
For inch conversions, you're on your own. ;-)
Your printer may print slightly smaller or larger, depending on the resolution and calibration. Try one, then scale appropriatey.