Holmes UH311 Replacement Filter 1 UH-311 replacement water purification filter for Holmes ultrasonic humidifiers Fits models HM-460/460B, HM-461, HM-455, HM-480, and HM-485 Traps impurities leaving humidifier moisture healthier Features antimicrobial protection to inhibit mold, mildew, and bacteria Measures 4-1/4 by 3-1/4 by 1-5/8 inches