This is a mold to vacuum form a version of the Montana Mask n95 style mask. Check the PDF files for assembly instructions as well as an information sheet that can be included with each mask for care and use instructions.
I printed this in PETG, which has higher temperature resistance than PLA, for better performance in the vacuum former/thermoformer. I also printed with 50 percent infill for greater resistance to the heat and pressure of the vacuum former.
Depending on the size of your machine, you can print more than one mold to make multiple masks per plastic sheet.