This Di2 specific post contains a sleeve that enables the Shimano DI2 battery to be housed in the seat post. The seat post battery option saves weight over the external battery and makes for a super-clean install on bikes designed for internal di2 cable routing. Battery sold separately.
The FSA K-Force Lite seatpost is both strong and elegant. The one-piece monocoque carbon construction provides a simple and refined appearance with smooth lines, because it is all carbon - not an aluminum head bonded to a carbon shaft. No bonding means a potential weak link is eliminated. The 25mm of setback is the most commonly sought after for the proper fit for most riders.
The gloss unidirectional carbon looks great on any bike. Maximum insertion line to saddle rails is 250mm with a minimum of 100mm required to be in the frame.