Those totally un-cool arm sleeves that were first worn by professional bicycle riders because they ride from low valleys (hot temps) up to mountain tops (much colder). These removable sleeves can be rolled down to the wrist, or removed & kept in a pocket.
Lately, runners and all sorts of athletes (term used loosely) are wearing these things. Very not cool. Who the hell do you think you are, Lance Armstrong??
While trail running the other day with friends, we saw 2 dudes wearing arm panties. We followed them for miles and gave them un-ending shit.