The media used in Multi-Flo Series S is composed of 100% synthetic fibers. These synthetic fibers are formed into a dual stage graded-density mat which ensures full depth loading, high dust holding capacity, and total media utilization. Also, these synthetic microfibers exhibit extraordinary strength and will not shed, even in high moisture applications or other adverse conditions. The media is supported downstream by a layer of spun-bonded synthetic. Multi-Flo Series S is available in four ASHRAE efficiency ranges (MERV 11-15) to meet the unique demands of every application.