Grade C Fine porosity, fast flow rate, with a 1.2um size particle retention. Primarily used for RIA procedures and harvesting lymphocytes. Glass microfiber filters are produced from 100% borosilicate glass microfiber without the use of binders or strengthening agents. Depth filtration categorizes filter media that traps particulate within the random matrix of fibers found within the thickness of the media. The efficiency rating of the filter is characteristic of the complex void space structure that develops as the fibers overlap. The fibers used to manufacture these depth filters are smooth and uniform. This permits their characteristically high flow rates while allowing retention of exceptionally small particles and high load capacity.