3M model #5P71 pre filter for use with 3M model #5000, 6000 and 7000 series respirators. Prefilters are used to help prolonge the life of the respirator by trapping dust, mists and particles. P95 filter is oil proof and 95% efficient. 10 filters per package. These prefilters must be used with 3M #501 filter retainer, which is sold separately.