Filter inside low flow modules 800518 & 800519 Back Catalog number: 201119 Manufacturer: SENSIDYNE Availability: In the manufacturer's stock Price on request - + Recommended 811-1004-01 PM-2.5 Impactor Kit, Replacement for Models 810-10 Price on request 910-0914-NO-R GilAir-Plus Data Logging 3-Pump Starter Kit, Bluet Price on request 800450 Soap Solution, Flow Cell (8 oz.), Gilibrator/Gilib Price on request