Gilson offers a selection of qualitative filter papers and grades for use in different extraction methods. The high-purity, low-ash papers can be used with a centrifuge, vacuum, and reflux extractors in asphalt mix design testing. They offer consistent performance and also perform well in gravimetric analysis, soil testing, and other applications. Available grades include 613, 617, 627, 633, 904 and 923. Filter papers are available with outside diameters ranging from 9.75 to 15.7in (248 to 399mm). Papers up to 12.25in have one middle filter hole, while those between 13 and 15.7in have no filter hole. Select the appropriate filter paper for your application based on diameter, hole, grade, flow rate, filter speed, and micron retention.