3M 2138 P3R (nuisance level organic vapour and acid gas) particulate Filters. Stand alone, lightweight particulate Filters, Lightweight, Low breathing resistance, Bayonet fitting system ensures precise and safe locking, Versatility: can be used on all 3M 6000, 7000 and 7500 Series Half Masks and Full Face Masks 1 Box 20 Filters (NOT PAIRS).