Axtron PP Sediment Filter 0.3 Micron 180gm - Made in Vietnam !! Axtron 0.3 Micron PP Sediment Filters are ultra-fine pre-filters designed to remove very small suspended particles from water before it reaches carbon filters and the RO membrane. With a much finer filtration level than standard sediment filters, these cartridges help improve overall water quality and protect your RO system from early damage.