The 2-speed bottom bracket gearbox “Doppio” from Kappstein is a compact, light and comfortable transmission unit in the bottom bracket bearing. Thanks to the extremely compact design, the entire gearbox is only 1cm wide and only about 200g heavier than conventional bottom brackets. The Doppio offers the driver a ratio of 1.57 in the heavier 2nd gear. This allows the number of gears to be increased with many possible combinations.