Anyone bought one?
Essentially masks don't protect you. Respirators do.
I had a look at the 3M 6500QL. 2 * P100 cartridges, they last indefinitely (they get clogged with cack and then you have to change them.)
Drawbacks?
It's half-face, and eyes are an infection route but apparently a minor one.
E.g., for flights, and other situations when trapped with people likely to be infectious for a long period of time.
attached photo (with goggles, which are ideal but I'm not sure)