GE Healthcare offers three grades of hardened ashless quantitative cellulose filter papers. Each grade offers a convenient combination of filtration speed and particle retention. They are available in different filter sizes, from small circle formats to large size sheets. We can also make custom-sized filters to meet your specific needs.Whatman hardened ashless quantitative filter papers are acid-hardened to give high wet strength and chemical resistance with extremely low ash content. They are suitable for a wide range of critical filtration procedures.