Dri-Eaz 4-PRO Dehumidifier filters are specially designed to work efficiently with Dri-Eaz dehumidifiers for restoration, remediation and construction. They help ensure proper operation and protect the working environment, plus its sturdy aluminum frame resists collapse and maintains proper filtration. Protect with four unique layers of filter media. Filters are not reusable. Replace whenever filter appears dirty or heavily loaded with particles.