I could not find a decent fitting arm file for my particular glasses/head combination so here is a customiser.

The customiser supports producing only the hinge to test your measurements as even with digital callipers this can be fiddly to get right.

Creality

Ender 3

No

No

0.12

20%

No supports required. Once printed I used a flat metal spade tool and a heat gun to heat the spade up then gently rub it over the surface to make it nice and smooth. Printing the arms separately also ensures no stringing between the arms.