Fits Hamilton Beach cool mist humidifier models 05520 and 05521. * Hamilton Beach humidifier wick replacement filters. * Measures approximately 6 1/2" H x 4 1/2" ID x 6 1/2" OD x 1" Thick. * With antimicrobial agent! * For optimum performance, replace filter at the beginning of each season or every 2 months depending on use.