John Cobb’s niche in the market of understanding rider needs in relation to performance and aerodynamics, led him to the design of the new rear mount water system that is optional with Cobb saddles*.
With this design, Cobb eliminates the hassle of needing several brackets, screws and clamps with its aerodynamically developed rear bracket. John Cobb spent several hours in the Texas A&M wind tunnel working out the best placement for the bottles, to allow the lowest drag of any rear bottle system. The new system will mount either one or two bottle cages. The rear bracket also makes a great transition rack mount and has convenient slots for holding your spare kit. This bracket completely clears up the bottom side of the saddle making it cleaner for better airflow under the rider while allowing for much easier seat adjustments on the bike.

* The rear mount water system is currently only available for the Fifty-Five JOF, the Randee, the Plus2 and the Gen 2, but will be available for all models in the future.
– See more at: http://www.cobbcycling.com/shop/accessories/rear-mount-water-system#sthash.46BFz8qQ.dpuf

Installation instructions are at the above website too.