The Robinair 34379 filter-drier has been specifically formulated using XH9 drier desicant to trap acid and particulates and is formulated to remove water from the refrigerant. DO NOT accept look alike or knock off filters. You must regularly change the 34379 filter-drier to assure adequate moisture and contaminant removal. Typically, you can recycle up to 150 pounds of R-134a refrigerant between filter changes.