This lightweight base layer is best used in temps around 40 degrees Fahrenheit. Any colder and you need the next layer in the series. The one feature I like about these is the ankle band. I have a pair of REI base layer pants and the ankle band is not flexible at all. The Patagonia pair stretches at the ankle band and anywhere else you need.
This review was written in the old system and had content requirements that are different than reviews written today.