The Craft Men's Pro Wool Extreme X Longsleeve Baselayer is an excellent lightweight long sleeve option. Wicks sweat well, fits nice and snug, and has longer sleeves which is excellent for someone with long arms.
It keeps me warm, very soft. It stretches a lot, so I sized down. Wash and hang dry. Dries quickly. Craft is always good quality.
I am somewhat between sizes and this one is a bit large so I am loosing some of the efficiency.
I have owned many Craft under layers. The quality is always great. The addition of Merino wool to the long sleeve makes it better than ever.
