Optrel 4088.410 - Swiss Air Pre-filter - Pack of 50
Noz-Alls stock pre-filters in packs of 50 but also in split packs for the smaller user. Regular replacement of your pre-filter will help to prolong the life of your main filter. Noz-Alls recommend that for heavily contaminated areas and to help provide for extra filtering you can use two prefilters which should extend the life of the main filter.