Filtex Bag 12 gal (Airvac) Central Vacuum Lrg Capacity (4)
Filtex (or Filtrex) and others. Replaces all Filtex bags about 18 inches tall and taller. Filter S-310. Top of bag has 1.25 inch round cardboard lip and 13.5 inch total diameter. (The variation over the years is due to changing bag manufacturers.)
Also fits some units made by: M&S, M & S