INCLUDES: (2pk) Inner Air Filter ( MERV Rating 11 ) and (2pk) Outer Air Filter ( MERV Rating 10 ) FUNCTION: Used to improve overall air quality while creating a more breathable atmosphere for your workshop, and keeps clean OUTER FILTER FILTRATION GRADE: 5 micron melt-blown non-woven filter paper intercepts unwanted particles that are 5 microns or larger – generating a consistent level of air purity INNER FILTER FILTRATION GRADE: Effectively cleans the air and removes airborne particles down to 1 micron in size COMPATIBILITY: Compatiblewith WEN 3410, Fox W1830, AF4000 & AF4001, Rikon 62-400, Grizzly G0738 & others with similar sized outer filters (check your system specifications). for WEN 90243-027-2 outer air filters and 90243-026-2 inner air filters