Brush drive turbine transmission for 6 brush All Terrain, Dual V, and V2 SteamVacs. Models include F7485-900 Series. This fan drive system is what powers the 6 rotating brushes. Fairly reliable. If locked up due to rust, the brushes wont turn. OEM Hoover. Helpful Hint: After cleaning of carpets and clean-up of machine...store dirty water tank OFF the machine for a few days to prevent moist chemical air being trapped in turbine system.