this is a little helper to adapt filter foils to mono- and binoculars

inner diameter of the connection surface is 83.5mm

i include the CAD files to change if you want or have to edit that
The CAD is really quick and easy

Probably this can work for cameras as well, but that depends on the geometries

print the TPU Part out of flexible material (such as TPU haha)
the solid part can be printed out of any material you have, i took PETG for the parts on the pictures

to assemble:

• use the TPU Part as a cutting template for the filter
• insert the filter to the solid part
• stick in the TPU part
• done
  

then you can stick the assembly to your binoculars and enjoy the new filter

Update:

TPU-V1 was a snug-fit to the binoculars, therefore we made the V2 with little venting holes, faced backwards

(Pictures show V1)

This model fits to “Skymaster 25x70” binoculars

we used AstroSolar Safety foil for the Pictures

WARNING:
be sure that the assemble fit safely to your binoculars, if you loos the filter, eg for sunlight, and you look into a light source without, it can hurt you!