Allegro Portable Fume Extractor Replacement Filters. This is for a Replacement Pre- Filter. The Specialty Aluminum Mesh Pre-Filter replacement for either Portable Fume Rxtractor Filter. Allegro's Filters and Pre Filters are offered in six different combinations and allow maximum flexibility for varying work applications (including HEPA for Hexavalent chromium control and 95% for carbon steel weld fumes). All filters are made in the USA.