i did it for mine OnePlus3 and the internal size is for OnePlus3 + Ringke Cover (this one http://fave.co/2eiSmRx) but it work with other similar cover too, of course.
To complete u need #4 magnets 4x2 mm.
I suggest to print in vertical (see the shot) at 0,15 or 0,20.
frame.stl | 533.7KB | |
locker.stl | 164.7KB |