The One and Only
I don't know if I can say anything about these layers that hasn't already been said, but these are the BEST baselayers created. Really Patagonia's capeline entirely is fantastic, but I use the 2 the most because of it's versatility. They breath like a champ, wick sweat rapidly, are thermally efficient, and are tremendously light and comfortable. They are indispensable in my skiing and fall backpacking wardrobes and they are the only layers I bring out on trail.