Bosch PowerTube batteries are integrated into the bike frame protecting them from the elements and concealing them from view. They are available for with the plug positioned for vertical or horizontal installation within the downtube, which allows for a narrower or wider cross section when viewed from above. **Horizontal and Vertical batteries are NOT interchangeable ***Powertube 625 batteries are larger than the 400 and 500 batteries and are compatible only with frames designed for the 625