The lightweight 3M 2128 P2R (nuisance level organic vapour and acid gas) particulate filters offer:* Low breathing resistance.* A bayonet fitting system to ensure precise and safe locking.* Versatility: can be used on all 3M 6000, 7000 and 7500 Series of Half Masks and Full Face Masks.* Maximum use concentration: 10xWEL1 BOX = 20 FILTERS (NOT PAIRS)