A projector's air filter prevents dust from accumulating on the optical elements inside the projector. If you are replacing your lamp, it is a good time to replace your filter. Manufacturers' suggest replacing the filter when changing the lamp to ensure optimal performance. The [phone removed by eBay] filter is compatible with the CHRISTIE DHD800 || EIKI EIP-HDT30 || SANYO PDG-DHT8000, PDG-DHT8000L projectors.