William - the D series was made to compete with the Miele S5. It is slightly larger than the Miele S5 by the body, has a longer hose and a 12 metre cable - nearly twice as much power cable than standard Miele S5 machines. The video link Mieles7 has provided here is a good one although I would never consider picking up beans with a hard floor tool. That's what the hose and smaller tools are for - but then that's me.
The D4 Premium essentially replaces the entire C cylinder vacuums Sebo used to make, so it's not a commercial vacuum although Sebo have since brought out a D Professional machine solely for commercial use and has a removable manual winder cord instead of auto rewind.
