Most versatile baselayer for most conditions - Rab Merino+ 120 Long Sleeve Zip Tee - Men's

I've used this baselayer for temps from upper teens to upper 80's; sunny weather to outer bands of a hurricane, on the Appalachian Trail, Chilean Desert, and the Peruvean Andes. And over the decades, I've tried most other baselayers. This is my go-to base layer most of the time. It keeps me warm when I need it, wicks mositure like crazy and dries fast. It incorporates the best of merino wool and synthetics at a weight that works well for most conditions. I have three of them.