The free loop on my casio broke recently so I needed a replacement. I've worn this part 24/7 for the past week so it hasn't broke or slipped off. My casio is a F-108WH for reference.

The interior dimensions are 19.0 x 6.2 mm. I made it 1 mm thick so its flexible enough to fit on the strap but strong enough not to slip off accidentally. The whole thing was extruded at 10 mm.

V3 Can be printed without supports. V2 Needs supports but was made to immitate the original free loop.

I recommend printing with a brim at slower settings to get better results. Infill shouldn't matter too much.