10 Pack of N 99 Filters provide 99% efficiency. Requires Filter Base Item N750015 when used alone (not part of this order). Efficient for Non-oil based aerosol particulates. North offers a complete line of cartridges and filters for the North 5500, 7700, 5400 and 7600 Series face pieces. All cartridges and filters listed below are interchangeable with any of these masks. Filters for Limited Use respirators, canisters for gas masks, and PAPR cartridges are listed in this catalog with those products. Ships per 10 pack in box. All North Cartridges & Filters are interchangeable for the North 5400, 5500, 7600 and 7700 Series Face pieces.