For those interested, this site has the lowest prices I've found for the new joint service M50 gas mask. Brand new...not surplus with expired components or filters, or stolen from the military.

Just bought two...great service and masks arrived in pristine condition seal in plastic from the factory... They are a lot of money, but still a better value than buying some imported (or used) piece of junk that probably won't even work when you need it. Breathing resistance and FOV is MUCH better than the old M40 I used in the Corps.

http://www.AGTtactical.com