Ahlstrom 992 is a fast filtering grade with a creped surface and high loading capacity. Flow rate: high. Retention: 43 microns. Ahlstrom offers a complete range of low ash filter papers for general laboratory work that provides you with the correct combination of particle retention, filtration speed, loading capacity and wet-strength. All our qualitative grades consist of > 95% super refined α-cellulose and linter fibers.