Replacement lens cap for an SLR camera (the design is based on a Canon lens cap). The cap is designed to fit on a lens with an inside diameter of 51mm.
If you what a different size then just measure the inside diameter of your camera & let me know - I'll upload a model of that size here. I created a parametric model in Solid Works so I just need to change one variable to generate a different size lens.
The SW files are on GrabCAD if you'd like a copy.
I printed the cap section at 0.2mm, and the inside part at 0.15mm - but I'm sure you could print successfully at a lower resolution and do a little trimming with a craft knife.
The tolerances are really small on this design so you'll probably need to do a little sanding with a fine file or sandpaper to get the inner ring in place.