The 3M 6099 Filters protect against organic vapours (boiling point above 65°C, inorganic vapours, acid gases, ammonia and its derivatives, mercury, formaldehyde up to 10ppm and particulatesFilters are specially designed and shaped to give "swept-back" position to enable excellent field of vision and balance. Lightweight , Low breathing resistance , Well balanced when fitted to a mask , Provides excellent field of vision as a result of the unique trapezoidal shape , Bayonet fitting system ensures precise and secure lockingStandard: EN14387 Approval: CE marked Maximum use concentration when used with full face masks: 20xWEL for organic vapours, inorganic, acid gases and ammonia; particulates up to 40xWEL - Only for full face masks, For use with Full face Masks Only ,1 BOX = 4 FILTERS (NOT PAIRS)