I didn't find a similar protection to the GoPro8 that could hold the Polar ND filter as well so I decided to do my own.

Please look at the picture to have an idea of what ND filters I have.

The fit is very tight, but both the GoPro and the filter can go in and out.

It's to be printed in TPU, since you have to pull some parts to fit the GoPro and to pull out the filter after it has been in place.

Turn the model on the flat side, the side where the ND filter enters to print. In my printer I don't need supports, or raft or anything. The design was made to take as little material as possible, to print without supports, and to print fast but still provide good quality.