Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4244383.

Some of my modifications to the excellent mask:

1. mask with more holes for heavier filters, i found out that i couldn't breathe through the vacuum cleaner bag filter with so small a surface as the original. Doesn't need an internal grid, the filter is locked between cap and mask.

2. slim cap with matching holes, great if you have a slim layer filter, like vacuum bags to lock in place

3. deeper cap for sponge type filters, with big opening too

4. a bayonet connector, tested with some proper commercial 3M filters, it connects properly

5. Cap with bayonet connector, you can use this with industrial commercial filters if you have those without the need to mod them. This makes the mask more useful. Tested with 3M P3 round filters

6. Cap with Bayonet connector, scaled 90% (ofc the bayonet had to stay the same) for smaller faces.

7. A small three holes buckle to tie the mask. We use 5mm wide elastic band for home diy and sewing, you can find that in almost any supermarket.

The bayonet cap needs to be printed with supports