not really a problem when you simply grab a new set as needed from the military supply truck, but could be a major problem during an emergency when these become nearly impossible to obtain (by anyone other than US Military personnel). Many see this as an improvement (which ultimately it is, however, you lose the ability to utilize standard 40mm NATO filter canisters which are most readily available). The idea is to replace a standard single filter configuration with a split filter canister solution that divides the weight between the 2 sides & reduces breathing resistance. Avon Protection has designed these to fit tightly against the facepiece with absolutely no gaps between the filter and surface of the gasmask. NOTE: These cannot be used with the any mask other than the M50 Will NOT work with C50, S10, FM12, FM53, M53, PCM50, etc. These Primary Filters (M41/M61) are designed to work with the Avon M50 Protective Gas Mask & utilize a proprietary connection type. You will receive sealed new in pkg / NIB item(s) only. Avon M50 Gas Mask Primary Filter Vacuum Sealed M61 US Mil-Spec NEW/Sealed as issued by Avon / US Military, Test Date(s): 2022* (see more info below) Fits US Military JSGPM M50 Protective Mask ONLY - Avon p/n 71024/1 Assembly - Primary Filter (PAIR) - New, Factory Sealed in Green Foil, contains 2 filters/pkg (Left & Right) NSN# 4240-0 This listing is for 1 package containing 2 filters (one complete set) Vacuum Sealed/Perfect & Unopened Note: The open filters shown in picture (filters out of the package) were used for photos only. Item: 324116265691 Avon M50 Gas Mask Primary Filter Vacuum Sealed M61 US Mil-Spec NEW/Sealed.