AlorAir MERV-1 Filter Replacement Set for Crawl Spaces Dehumidifiers Sentinel HD55P 4 Pack Dimensions: 9.76 x10.62 x1.8in, Compatible with: Sentinel HD55P MERV-1 filter captures the majority of "larger" dust after the air blew into the machine. It can protect the inner component from the congestion of impurities from the air taking in from outside Also at the same time ensure the maximum airflow supply volume