Foam Replacement Pre-Filter Humidifier 326 Bionaire (Aftermarket) Fits Bionaire models CM-2, CM-2S, CM-2.5, CM-3, CM-3S, CM-3SW, CM-4, CM-4S, CM-6, CM-0210, CMP-3, CMP-5, CP-305, CP-315, CP-0210, CP-0260, CP-0310, CP-0315, CP-0470 and #14094. Bionaire foam pre-filter. Measures approximately 5 1/4" x 7 1/4". For optimum performance, replace filter every 3 months. This is an aftermarket filter.