What is the Shimano Dura-Ace FD-R9150 Di2 braze-on adaptor?

This is the braze-on seat tube adaptor for the Shimano Dura-Ace FD-R9150 Di2 front derailleur, allowing the braze-on style derailleur to mount on frames with 28.6mm or 31.8mm round seat tubes. Some frames are built for band-clamp front derailleur attachment rather than braze-on tabs, and this adaptor bridges the gap -- letting riders run a braze-on Di2 front derailleur on frames that would otherwise require a clamp-on unit. A small but necessary piece of hardware for certain frame and groupset combinations.

Compatible with Shimano Dura-Ace FD-R9150 Di2 front derailleur. Fits 28.6mm and 31.8mm seat tube diameters. Verify your frame's seat tube diameter and front derailleur mount type before ordering.