Earbud storage case, in two sizes. The 3.5mm versions have slots for the 3.5mm jack. (added a large and XL versions, but haven't tried printing them)
The first 0.4mm works as a hinge, I used clear PET for the first couple of layers since it work better as a hinge material and works as a window, but ABS will work too. Take a look at the picture with the orange cases to see how it works.