3 pack Filter For use with iRobot Roomba 500 or 600 Series : ex: 550 560 650 620 etc Changing filter every 2 - 3 months recommended (Varies dependent on environment / use). Remove dustbin and slide filter out to clean or change. Filters maintain optimal cleaning performance. Filters reduce infiltration of dust, pollen and other allergens. Prevents dust and dirt from escaping vacuum system.