When converting to Di2 from a standard cable based setup, holes are left in the down tube, the seat tube, the bottom bracket, and the rear derailleur cable exit. The holes can let water and debris enter the frame and bottom bracket, which can contaminate the bearings and damage internal Di2 cable connections. This kit closes all of those holes to form a water resistant barrier.
The bottom bracket cap replaces the plastic cable guide that falls out when the shift cables are removed. The rear derailleur grommet replaces the cable grommet in the rear to prevent the wire from resting directly on bare metal. The down tube and seat tube strain reliefs prevent the wires from rubbing on bare metal and close the holes. The down tube plugs and bottom bracket cap form a water tight seal for the bottom bracket that will prevent contaminants from entering the inside of the frame.
Weight: < 3g
When installing the bottom bracket cap, always attach it from the rear of the bike first (hook back, clip front). Gently clip in the front using your thumb as shown in the pictures. If not installed correctly, the tab can break. This is due to the angle the hole is cut in the frame.
To remove the BB cap, use the small ridge in the rear center of the cap, to pop off the rear of the cap first. This is the opposite direction used in the installation. The front of the cap faces the front of the bike and is indicated by arrows on the inside.
When installing the rear strain grommet, spread it enough to slip it over the wire and use the wire to help pull it snugly into the hole while pushing the plug in. Use the reverse process to remove it.