Needed a solar filter for my camera Olympus SP-550UZ. Used 2 layers top and bottom and 2-3 vertical layers. Layer height is .4. I didn't get any good pictures of the August eclipse, but that was me not the camera. you can get some 2mm foam from a craft store that is sticky on one side. i used that to line the inside of the box and to make a tight fit for the filter and camera. With the foam installed it's a 40mm diameter.