Filter inside low flow modules 800518 & 800519 Back Catalog number: 201119 Manufacturer: SENSIDYNE Availability: In the manufacturer's stock Price on request - + Recommended 385-0112-01 Sheath Air Purge Flow Filter for Nephelometer Price on request 360-0201-01 Operation Manual/Software CD for Deluxe Nephelomet Price on request 811-1004-02 PM-10 Impactor Kit, Replacement for Models 810-100 Price on request