Super sleek looking pouch that fits the essentials for changing a tire. Hard to speak on the aero benefit, but it looks the part.
Small catch though, it makes the bottle significantly harder to get out and in. No issue if you only access the bottle once or twice a ride, but this would be a no-go in my opinion if it was your main drinking source. In my case, its not so I luck out.
As a previous reviewer mentioned, at first when adding this to a gorilla cage it is almost impossible to remove a bottle while riding. After leaving an oversized bottle in the cagepouch for 3 days, the holder has loosened and it is possible to remove a bottle while riding. As far as space, I have 1 16g CO2, 1 nozle, multitool kit, 2 tire levers, tube, valve core wrench, tubeliss tire patch kit, and chain quicklink in the bag. There is still a little space left, but not much.