Wick filters designed to fit select evaporative humidifiers. treated. The filter must have the correct height, width, thickness, and material for maximum performance. wicks are developed from the highest quality materials that work to absorb the maximum amount of water while filtering the circulating air. No cleaning required, disposable design. Replace every 4 to 8 weeks, depending on use. Compatible with Models Evap1, Evap2, Evap3, and Evap40.