Whatman filter papers are world-renowned as the standard for laboratory filtration and are associated with quality, reliability and customer service. Manufactured from high-quality cotton linters, which have been treated to achieve a minimum alpha cellulose contact of 98%. Used for general filtration and exhibit particle retention levels down to 2.5 µm. Used in qualitative analytical techniques to determine and identify materials. Offers a wide choice of retention/flow rate combinations to suit numerous laboratory applications. The different groups of cellulose filters offer increasing degrees of purity, hardness and chemical resistance. Prepleated filters are also available, which give improved flow rate and increased loading capacity compared - Filter Circles, 21mm Dia, Hardened Ashless Grade 540, 100/pk 14-21 Days