Wow is about all that needs to be said here. This shirt pretty much replaces every other article of clothing I USED to use as a base layer. I use this primarily for winter cycling and snowboarding. At 15 degrees, this shirt with just a thin, windproof and lightly insulated cycling jacket is perfect. While snowboarding, this shirt with just my snowboarding jacket over the top is money for a full day on the mountain. The 260 is a bit warm for heavy activity in anything but winter cold in my opinion, so if you're looking for a base layer for fall/spring, consider the same shirt in a 200 (which I also have). The greatest thing about this shirt, is that it can be worn for days on end (I literally ride in it 4-5 days a week, and only wash it once. It holds ZERO odor. Merino wool is where it's at, and Icebreaker is probably the best you can buy. One more thing worth mentioning about the 260, is that it fits a bit more loosely than the 200, so you could easily wear it on its own if you're OK with a "slim fit". I'm 5'8, 160 with an athletic build, and the medium fits perfectly. Icebreaker puts out some fantastic pieces, and this is certainly no exception. Buy it without hesitation.