The Carbon Seat Bottle Cage Mount allows you to mount two cages on your carbon seat while drilling only two small holes in the center of the seat, where they are away from the edge and much less likely to propogate a crack in the event of an accident.
The bracket is normally held firmly in place by your weight, but when necessary, the mount flexes, protecting the seat and possibly also, the cage. I was quite upset recently to find my CA2 had fallen over in the garage. I found only a few small scuffs on the edge of my nice carbon cage. The bracket had flexed and protected the cage from serious damage.
Two standard sizes of the bracket:
Current Bacchetta carbon seats are just under 9" wide. The Small bracket is sized for the Bacchetta seats. (note older Bacchetta seats are wider)
M5 seats measure approximately 9.625" wide. The Medium bracket is sized for the M5 seats.
All brackets provide 1/4" clearance on the stated size.