Pack of 4 premium carbon pre-filter absorbs and eliminates household odorFor use with Holmes air purification models: HAP2400, HAP242, HAP9240, HAP9242, HAP412, HAP9412 and HAP9414 require 1 filter.HAP422, HAP424, HAP9422 and HAP9424 require 2 filters9.5 inch (L) x 4 inch (W). Cannot be used independently of the main purification filter. The set includes 4 pre-filters. Directly apply to Aer1 Filter Premium Carbon Filter absorbs and eliminates odors from pets, nurseries, kitchen, garbage or litter box. Color: black Material: sponge Package contents: 4 * carbon sponge Only the above package content, other products are not included. Note: light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement error is +/- 1-3cm.