The 19776 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 change the filter-drier to assure adequate moisture and contaminant removal. Typically, you can recycle up to 300 pounds (136 kilograms) of R-134a or 600 pounds (272 kilograms) of refrigerant between filter changes. To help you know when you’ve reached that point, the unit displays the warning message prompting you to change the filter drier.