Honeywell HRF-D1 Universal HEPA filter, HRF-D1 / Filter (D) Captures up to 99.97% of airborne particles at 0.3 microns Package includes 1 filter, which should be replaced every 3 to 5 years. Certain models may require more than 1 D filter; please check your OM for filter requirements Use with Honeywell model series: 10500, 10590, 17000 and 50100 Replacement Filter D (replaces HRF-11) To ensure stated product performance, use only Certified Honeywell Replacement Filters.