Honeywell, Filter A, Universal Activated Carbon Pre Filter, Helps Reduce Common Household Odors, Traps More Dirt Particles Than Standard Carbon Filters, Therefore, Maximizing Hepa Filter Life, Replace Approximately Every 3 Months, Fits All Round Honeywell Air Cleaners, #17000 Series, #18150 Series, #40100 Series & #40200 Series, For Use With Model #17000-S, HPA104, TV #179-978.