Hi, The Fuller Brush FB90 and the FB90t vacuums will also take Riccar 4000 series vacuum bags. The Fuller Brush company, and the Riccar companies are owned fully by their parent company, Tacony USA. The Riccar 4000 bags are going to be the cheapest bag per bag for you to buy. We have several items for the Riccar 4000 series bags, Here are the links to our http://www.govacuum.com website and the differences between them; Riccar 4000 Series Upright bags Standard Paper Bags, with an electrostatically charged inner bag liner that captures the fine mircoscopic dust particles. Genuine Riccar (Fuller Brush) bags; 6 Pack for $9.95; and 12 pack for $16.99 http://www.govacuum.com/riccar-2000-4000-and-vibrance-series-filter-vacuum-bag-antimicrobial-12-pk.html Riccar 4000 Series upright bags made by Envirocare. Similar microfiltration inner liner; 12 Pack for $10.95 Riccar 4000 Series HEPA Filtration bags, genuine. These bags are the best quality bags available for your Fuller Brush. These bags are a cloth type disposable bag, which is 99.97% efficient down to .3 microns (HEPA Certified). Hope this helps.