I use these on warmer days and when I'm touring. They do a great job keeping me warm, but I never overheat in them. They do a great job regulating temperature, wicking away perspiration, and they don't absorb odor either. My only complaint is that I like a really tight fit with baselayers, and they fit well except around the ankles, they are a tiny bit loose. Otherwise, these are great.

Wore these along with the 1/4 zip top (not sold here, unfortunately) during a mid-October weekend in the Adirondack High Peaks region. Under a pair of hiking pants, these will be all you need in fair weather and temperatures ranging from the low 50s to right down around freezing. While active, the top is all you need for similar weather. My only gripe is that the size I got (medium) were a bit short on me in length. If you're around 5'10" and about 145-160ish, consider ordering a size up. Other than that, the material is very lightweight, extremely breathable, and dries very quickly - everything you ask for in a lightweight base layer.

I wanted a base layer that I could wear outside and yet be comfortable when inside. It has been single digits this week in Chicago, and I have been comfortable wearing these while walking to the train (about a half mile) and then leaving them on, under my suit pants, during the day in the office. Looking forward to wearing them on a backpacking trip too.

I took these to a recent snowboard trip to Colorado. The temperatures were in the 30-40s. My legs were plenty warm (and sweatfree) when worn under snowboard pants. I'm 5'7", 160 lbs and a medium was a nice, snug fit. If the temperatures were a little colder I think I would have needed something a little thicker.