This cap is designed to fit on the back of Nikon F-Mount lenses. Its design is quite close to the original and it is quite sturdy.
This cap's design is close to the original. It is very sturdy and fits tightly to F-Mount lenses. This is how you reach the best result:
1) Use PLA instead of ABS. I printed a few on a Makerbot Replicator and ABS tended to warp quite badly, while PLA came out perfect with this design. But maybe you're luckier. (I typically print this one with these settings: Infill 20%, PLA at 185Â°C extruder and 60Â°C heated plate.
2) If the print is fine, you NEED to get some fine sandpaper (120 or finer) and sand the part that goes to your lens until it fits. I'll add a version that will fit out of the box. For now, if you sand it to the right measure, it will fit perfectly and the surface will be very smooth.