Ultegra FD-6800 Front Derailleur Clamp Shim reduces 31.8mm to 28.6mm

Shimano Ultegra FD-6800 Front Derailleur Clamp Shim reduces 31.8mm to 28.6mm. Shimano Front Derailleur Seat Tube Shims

Derailleur = the size of the clamp on the front derailleur you have

Frame = the size of the seat tube the derailleur plus shim will fit