Non-sterile, gridded membrane filters can be used for colony counting, particle testing and microscopy. Before usage, the filters first need to be sterilized (e.g. by autoclaving at 121°C). The membrane filters are available in different pore sizes and three different material types. Cellulose nitrate filters (mixed cellulose ester) contain a mixture of cellulose nitrate and cellulose acetate, which assures effective retention combined with high flow rates and optimal colony growth. Cellulose acetate combines high flow rates and thermal stability with very low adsorption characteristics. The various filter colors allow the best possible contrast to the colonies or particles for easy and reliable quantification and identification. High flow membranes Three different colors The membrane filters are in accordance with the following norms: ISO 7704, ISO 7899-2, ISO 8199, ISO 9308-1 and EN 12780.