I ordered the mask cartridge TWICE and both times I received the elastic head strap instead of the cartridge.
Grab some extra flat cartridges for future use
I grabbed a few extra of the flat filter cartridges for my Gill Mask original as I find them fine for breathing and like the ability to cut my own filters as needed.
The mask has better facial than any other type easily sanitized comfortable to wear for hours at a time. It does produce a greater resistance to breathing due to the better seal which lifting weights strengthens respiratory muscles