If you're looking for carbon fiber bottle cages it simply doesn't get better than Arundel. These guys have been making them longer than almost everyone else. They are light and strong. While carbon cages certainly aren't guaranteed to last and are considered "race-level" equipment these will hold up better than just about any other carbon cage out there.
From the manufacturer: The Dave-O cage is perhaps iconic, as before 2001 bottle cages didn't look or work like this. A classic shape with superior performance. Dave-O's are still the benchmark of quality in carbon bottle cages.