3M 2135 P3R 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, Maximum use concentration: 20xWEL (half mask) or 40xWEL (full face mask), Standard: EN143 , Approval: CE marked, Workplace Exposure Limit 1 BOX = 20 FILTERS (NOT PAIRS)