For seat post ID24.5mm to 28mm or ID20mm to 23mm*Battery and cable not included*
Best Price: £12.59 from Cyclestore
M:part Di2 Seatpost Battery Mount Internal Post Diameter 20mm to 23mm Reviews
For seat post ID24.5mm to 28mm or ID20mm to 23mm*Battery and cable not included*
Best Price: £12.59 from Cyclestore