Sterile, individually wrapped membranes have a 0.45 µm pore size. They are made of cellulose nitrate (cellulose ester), a material that assures effective retention with high flow rates and optimum colony growth. The printed grid divides the filtration area into 130 squares (each measuring 3.1×3.1 mm) which makes the counting easier, especially for higher bacteria counts and for micro-colonies, but does not influence the growth. White membranes are most popular for enumerating general bacteria. Gray membranes turn black when wet for facilitating the detection of yeast and molds.
•Gamma irradiated, 25kGray
•No enhancement or inhibition by the grid lines