If you are looking for highest possible gears, high-speed-drive is your ultimate choice.

The standard chainring with 27 teeth -> equals a chainring with 67 teeth in high gear mode.
A chainring with 30 teeth -> equals a chainring with 75 teeth in high gear mode.
A chainring with 34 teeth -> equals a chainring with 85 teeth in high gear mode.
For very special applications there is an adapter for BCD 130 mm available, which allows to mount chainrings of 38 t. or bigger-> equals chainrings with 95t. (or bigger) in high gear mode.

Black bars in the diagram on the right show additional gears in combination of high-speed-drive with a 5-speed-hub.

Please find a gear range calculator (for meters per revolution) here:
-> in combination with derailleurs
-> in combination with internal hubs

Please find a gear range calculator (for gear inches) here:
-> in combination with derailleurs
-> in combination with internal hubs