The last mask filter was threaded for NATO and GOST filters, meaning the threads weren't exactly Ideal for the GP-5 mask/Warsaw act masks I had made it for, so I took bluepug's threads, thank you by the way, and made some quick fixes as well as adding some new hole shapes to let air in, I made all these fixes in Tinkercad online, so it isn't exactly professional level, but it works and looks good.
As for assembly you can simply superglue it together, use epoxy, anything that will stick to your filaments. You can also fill it with something like cotton to keep debris from getting in, but I suggest you put cloth or mesh at the bottom to keep it from coming out of the holes in the larger designs
Once I fix my nozzle and print another in white PLA I'll post pictures.
I had to re-upload this with pictures because the STL files were not displaying correctly