"This is the best piece in my clothing kit"
-I use this in winter and summer (and in between)-it's used as my baselayer with, maybe, a softshell over it and a hardshell if the snow is wet (I live in the PNW-great wicking ability and keeps me warm in the dead of winter during BC skiing. Even in -10C or 14F it is amazing how warm you remain (I do run hot)-in the summer, it wicks beautifully and is super thin so you don't overheat-this is one of my best pieces of kit
Nota bene: Merino is costly and demands an investment, so I bought the Merino 2 on a ridiculous sale. That said, if you're willing to pay up, this will pay off. The merino/polyester blend is isn't quite as soft as pure merino, but it wicks sweat and holds up better over time (especially if you're planning to run it through the wash). I usually wear a S in Patagonia, but I got an XS as a close-fitting baselayer. I wouldn't recommend this as an independent 1/4-zip unless you have a substantial tee under it (the material is pretty thin). But it captures body heat, and the zipper is really lightweight, so I layer it under an R1 or softshell for cold weather hiking.