The 0.25” diameter replacement filter cartridges are available in 0.2 micron, 0.5 micron, 2 micron, 10 micron and 20 micron porosity, and have a 0.32 cm² active area. Total internal volume is 11 µL for the 0.2 micron filter, 14 µL for the 0.5 micron filter, 18 µL for