The POWERTEC Outer Filter (for the POWERTEC AF4000, Shop Fox W1830, Rikon 62-4000, etc) allows your dust-collection system to operate at its peak efficiency and effectiveness. This high-performing and ultra-effective inner filter features a high dust-holding capacity, meaning that the dust, dirt and other airborne particles (as small as 3 microns!) are extracted and trapped in your filtration system and not released into the air that you breath. These handy filters are much more effective than fiberglass filters. Hard-working filters, pristine results! This premium filter makes certain that your workshop and/or home air-quality is clear, clean and optimally healthy. Hard-working filters, pristine results!