3M FILTER RETAINER 501: The 5N11 is a Pre-Filter to provide added Dust and Particulate protection to an organic cartridge (like the 6001 Organic Vapor Cartridge or others). To be used with 3M 5000 6000 and 7000 series respirators and requires the 3M-501 retainer ring for proper assembly. This prefilter offers cake-resistant filter media for easy breathing and lint-resistant coating to help ensure exacting results during painting operations. Requires N (non-oil) filters. Ideal for dust and larger airborne particles and will provide longer life for your vapor cartridges.