Ultrafine™ Replacement cartridge for ‘Original Housing Style’ Nature Pure® model (see housing picture attached). Ultrafine™ replacement cartridge is rated for 500 gallons, at a flow rate of 0.5 gallons per minute. Nature Pure® Ultrafine™ purifier does not require chemicals or electricity. This is the replacement cartridge only and includes a new shear rod. Coldwater use only.