It's a bottle holder. It's an aero bag holder. No, it's the Super Wing!
The XLAB Super Wing is a rear hydration and repair carrier that offers all of the same features as their revolutionary Carbon Wing, just easier on the budget and slightly heavier. Constructed from aerospace-grade aluminum alloy, the Super Wing just may be the toughest carrier on the market. Easily allowing for water bottles in 3 different placements and 4 different angles, the Super Wing is a versatile carrier that tucks away inside the aero pocket created by your body cutting through the wind. With this hydration and repair carrier doing the work, you can save up to 13 seconds over 40 kilometers.
B-Stock - This product has one or more B-Stock units available. These units can be purchased at a discount (see option select). B-Stock units were returned from other customers and may have missing or damaged packaging materials. These units are otherwise as new. The full manufacturer warranty applies. Click Here for more information.
Cage Material: Aluminum
Mfg PartNum: 1148
Solid construction. Easily carries two bottles and I have put three on there with no issues. Not sure if that is recommended or not, but it worked for me. Bottles sit fairly high compared to the other holders I have used behind the seat. This is theoretically more aero. Slightly more effort to get the leg over though. Using in combination with Fizik Mistica.