Controls coarse particles and eliminates micro-particles such as pollen, pet dander and mold spores. Patented knife edge seal technology ensures 100% of air flows through the filter with NO system leakage. Made with non-woven glass micro-fiber and non-off-gassing separators. Mini-pleated for high capacity and helps protect product's subsequent filters. Can last up to 18 months when unit on fan speed 3 for 10 hours a day. Swiss Made.