Filter inside low flow modules 800518 & 800519 Back Catalog number: 201119 Manufacturer: SENSIDYNE Availability: In the manufacturer's stock Price on request - + Recommended 811-0920-01 Replacement Valve Caps (Pack of 2) Price on request 385-0115-01 Nephelometer O-Ring, Replacement Price on request 783-0015-01 Lithium Ion Replacement Battery Pack for Nephelome Price on request