Simple tool to mask the sun when it's visible in the photo. Masking it avoids the sunflares so it's possible to compose two shots (one masked and one unmasked) and get a perfect sun photo without unwanted flares.
Easier than placing a finger in front of the camera.

This tool can be screwed to the lens just like any other photographic filter, but it's only available for 67mm lenses.

Along with the complete model there are arms with discs of different diameters. Larger discs are to be used with longer lenses. You can of course modify one of these arms to get larger or smaller discs for your specific needs.

Prusa

i3 MK2.5

No

No

0.15

100%

Do not use too low resolutions as the parts have small details. The suggested one is perfect for printing a good and usable model.
You can use PLA or PET, but avoid ABS because of the shrinking. Also it's better to print at slow speed.
For the color you can use whatever you want, but darker ones are surely the best choice.

After printing you may need to light sand the parts for better fitting. Note that the parts should not move too freely or the disc will not stay in place when shooting.
Look at the photos for assembly. Not too difficult. Take particular attention to the rings orientation.

When assembling the inner and the outer ring you may need to use some force, that's normal, but do not exaggerate to avoid damages.