I have two pairs of compression calf sleeves; one Zoot, one Zensah. The Zoots are much much tighter, and because of that, much harder to get on and off. The Zensahs aren't nearly as tight, and slip on and off easily. And surprisingly, I do notice a difference when I wear them, and both seem to have an equal effect. I don't wear them while I am working out, unless I am doing a track workout in spikes, because my calves tend to tighten up then, but wearing them after a workout or race and going to bed in them does make my legs feel a lot better. Maybe it's psychosomatic; I don't know. I don't think they improve performance any, but they sure help my legs recover faster.