North Safety R95 Prefilters have 95% efficiency for all particulates. Restricted to 8 hours service life if used in atmospheres containing oil-based aerosols. When used with N750027 filter covers and N750015 filter retainers, they will fit 5400, 5500, 7600 and 7700 Series Half Mask and Full Facepiece respirators when cartridges are not used.