We make Di2 battery holders for 25.4mm seat posts with various inside diameter size options. If you are using a seatpost not listed here, please contact us for assistance.
C2 - 19 mm ID (Carbon)
C3 - 19.5 mm ID (Aluminum)
SAVE - (unmodified)
BBB Basic - 19.65 mm ID (Aluminum)
SLK Carbon - 20.5 mm ID (Carbon)
Zipp Service Course SL Carbon - 22 mm mm ID (Carbon)
Ad hoc solutions using tape and foam have multiple issues. The net result is often a damaged or stuck battery.
Problems with Tape or Foam:
Removing the holder requires pliers. Never use pliers on the battery itself.
Attention EU Customers
Customers in the EU (European Union) should be aware that beginning July 1, 2020, Bup Labs will not be collecting VAT (Value Added Tax) charges. At this time, EU customers will be required to pay the VAT themselves to receive their shipments. The method will depend on the service chosen and country.