Go-Cal Replacent Filter Back Catalog number: 811-9917-01 Manufacturer: SENSIDYNE Availability: In the manufacturer's stock Price on request - + Recommended GF25TQ Filter, Tissue Quartz, (99.90% retention of 0.3µm Price on request 811-9927-03 Cyclone, BGI4L Replacement Screw Kit Price on request 385-0117-01 Tri-pod mounting bracket for Nephelometer (Tri-pod Price on request