This is a faithful re-creation of the Bendix 2-speed Automatic hubs found on so many Schwinns in the late 1960's. The rider back-pedals slightly to shift gears.
The YELLOW band hub has a low gear: 1 sprocket turn for .67 hub turn to go up hills easier. High gear is 1:1. The original Bendix hubs would go on bikes with 700c, 26", and 24" wheels.