Ive seen some of the russian gas masks for sale by HQ surplus for about $20 with filter, however there is a swiss or something one right next to it and it costs $70 or 80. I was wondering if there was much of difference in the perfomrance of these? Do they rate them by microns? Ive never had any experience with them. I figure for $20 you cant beat a possible good investment for a shtf bag/scenario.