Whatman WCN cellulose nitrate membrane filters pre-sterilized in gridded style. This grade is manufactured under strictly controlled cleanroom conditions. These sterile filter papers are primarily used in microbiological laboratory applications. Cellulose nitrate membrane filters are the standard filter for the majority of laboratory applications involving particles and cells in the range of 0.11¬µm to 5.0¬µm. These sterile filters are supplied individually packed, with or without an absorbent pad included, in sealed polyester envelopes. Factory sterilization is carried out using ethylene oxide gas. All filters are 47mm in diameter.