"Two layer brushed fabric combines enhanced thermal protection and moisture transport. Compression fit for bolstered muscle support and increased circulation resulting in higher efficiency output and increased stamina."In other words, it keeps you pretty warm!
"Anti-Odor Technology prevents the growth of odor causing microbes."And doesn't smell!
Here are some more reviews of the Under Armour cold gear
For more on winter running, here's a link from the February Runners World magazine