Credit for the original model to https://grabcad.com/library/wera-hex-driver-2mm-1.

This is a 2.5mm Allen key holder with the handle shape from a Wera screwdriver.

EDIT:

Having tested the beefed-up version I can confirm it works at 2.5mm, 3mm and 4mm. For sized 4mm and larger print the handle at 0.3mm layer heights but keep the bottom bit at 0.2 otherwise the threads can be too stringy.

I super glued the tip down once I was sure of the fit. This strengthened the tool but I don't believe is necessary.

This tool can be printed without supports but I chose to print it with supports as it improved the quality of the threads and they were printed at the same time.

I've included multiple files.

2.5 Wera - Wera - 2.5x75 - Copy-1.STL
2.5 Wera - Wera - 2.5x75-2.STL

These are the original 2 files and would probably work fine in PLA that holds tolerance better than PETG. I found the hex part of the handle was too tight so I chose to use the 3.0 version of these two files. They are just the same but have a larger hole (3 and 3.2 instead of 2.9).

Wera Bottom 3.STL
Wera Bottom 3.2.STL

Next, I have included an untested beefier version where the parts that I found to be weaker and breaking have been increased in thickness. Note that the outer dimensions are all the same. This could probably be scaled to be used with other sizes. Ie for a 4mm hex a scale of 160% should work. EDIT: THESE WORK BEST, USE THESE AND SCALE THEM UP.

2.5 WERA Beef - BEEFWera - 2.5x75-2.STL
2.5 WERA Beef - BEEFWera - 2.5x75 - Copy-1.STL