The Panasonic ET-EMF510 Eco Filter Replacement Unit is compatible with the Panasonic PT-DZ21K, PT-DS20K and PT-DW17K projectors. Depending on the usage environment, the Eco Filter does not need maintenance for up to 12,000 hours of projector use. The Eco Filter's micro cut design collects minute dust particles with an ion effect. It combines with the dust-resistant cabinet to enable long-term use even under harsh conditions. The environmental design lets you wash the filter with water and reuse it. Panasonic recommends replacing the filter with a new one after it has been washed and reused twice. If the filter is not sufficiently clean after washing, you should replace it with a new one.