Personally am not enamored of CF stems, posts and bars. If they fail you're pretty much screwed. Also good quality aluminum is frequently cheaper and weight differences are minimal.
Having said that there's alot of CF stems and etc. out there and they don't catastrophically fail on a daily basis and as for myself: I ride CF forks so my fear is not completely rational.
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“Life is not one damned thing after another. Life is one damned thing over and over.”
Edna St. Vincent Millay