You'll see that the E-Tube Di2 SM-BMR1 Battery Mount is available in three options -- Long External, Long Internal, and Short. Both the long versions mount from one of the water bottle mounts on the down or seat tube of your frame. However, they're designed to be paired specifically with either type of wiring kit you'll be using -- Internal or External.

The short version is designed to be used on bike frames that bear a specific Di2 battery mounting location on the chainstay or down tube, separate from the water bottle mounts. It can be used with internal or external wiring kits.

The Shimano E-Tube Di2 SM-BMR1 Battery Mount accepts the SM-BTR1 7.4 volt battery. Please Note: This is only the mount (battery not included).