Fits Holmes models HAP-290, 475, HAP-300, 3004, HAP-291, 2914, HAP-292, HAP-70, 293, 2934, 540, 541. This Universal Cut-to-Fit activated carbon pre-filter helps remove large particles and reduce common household odors such as cooking odors, tobacco smoke odors, pet odors, musty odors, etc. This large 15-3/4 x 48 cut-to-fit activated carbon sheet, makes 1 to 6 pre-filters depending on the model. For optimum performance, replace pre-filter every 2 to 3 months.