AfterMarket HAPF220 Holmes Carbon Air Cleaner Replacement Pre-Filter (2 Pack) Fits Holmes model HAP222, HAP223, and HAP2234. Filters Measure 4 1/2" x 8"x.2" 2 carbon pre-filters per pack For optimum performance, replace pre-filter every 2 to 3 months. Made in the USA BulkFilter Brand Filters