The only baselayer you should consider
I'd been looking all over for some baselayers to keep warm during the winter months and for my annual ski trips. I tried the standard 'long john's' and while they are very cheap and warm, the fabric was extremely itchy and just unbearable for anything over 5 minutes. I tried the Under Armour cold gear under a recommendation from a friend and it is absolutely the best decision i have made for keeping warm. It's super light and the 'fitted' version is snug enough to keep in contact with your skin (keeping you warm from ambient air temperatures) but not tight enough to be uncomfortable. The fabric they use in almost all their products dries very quickly after coming into contact with water/snow (if it happens to seep through your pants) even while wearing it so it doesn't retain a lot of water that will make you cold and miserable. The crew neck in this version is perfect for versatility as I've been able to wear it while snowboarding, sports, work and even under a dress shirt for outdoor formal events. It allows me to look professional without exposing the base layer that may potentially be against any uniform regulations you may have at your workplace. I'm approximately 5'9", 150 lbs, slim build and the small is spot on for me. And since it is a stretchable fabric, even if i bulk on another 10-15lbs, I'm sure the fit will still be comfortable.

Great
Was happy with the product and Altrec shipped quickly. Very satisfied.

great for cold weather
I use this mock to run in the early mornings and to go snowboarding. Keeps me very warm and dry.

Works Perfectly
I've used this shirt for ski touring in the alps. It really wicks away moisture effectively and provides sufficient warmth that only a vest is needed over the top.

Under Armour Men
Love it. Does what it claims.