P2 R D + Ozone particulate filter. In addition to the particle filtering efficiency these filters also offer protection against ozone; at 1000ppb ozone a maximum use time of 8h. P2 R D for protection against toxic dusts, fumes and water/oil based mists/aerosols 10 x WEL Revolutionary EasyLock filter system with no additional clips or holders. Different gas and particulate filters can be combined. EasyLock? particulate filters can either be connected to the EasyLock? gas cartridges or directly with the mask body. Any combination of filters possible, simply click together, there is no need for additional clips or filter holders. 1 BOX =12 FILTERS (NOT PAIRS)