Ummm, wool warm and soft.... - Smartwool PhD Wind Zip T Top - Mens

There is nothing that compares with a merino base layer for warmth and comfort. On below-freezing days and nights. Or when it's raining for days. Merino is instantly warming and never itchy. I buy a size larger than I would normally wear, and never worry about machine washing and drying (on low to med. heat).

The warmth to weight ratio of merino wool is amazing. It weighs little, but warms better than anything else I've tried. I fish the rivers in Alaska and merino is the best insulating base layer for wading cold rivers. Hiking and climbing the mountains in Idaho...merino breathes well and still keeps you warm. Highly recommended!!