F2 is our High-Flow filter, with 40% better breathability than RZĀ« standard F1 filter Electrostatic Filter, which traps particulates down to .1 micron in size Best-in-class filtration with 360-degree seal Surpasses the N95 standard, filtering up to 99.9% of particulates down to .1 micron in size (400 times smaller than a human hair) Common F2 use: High Intensity, Dust/pollen/cold air - No fumes/odors present Choose the filter size that matches mask size. FILTER F2 HIGHFLO LG 12PK