Lululemon Core Half-Zip

Layering properly is tough in the cold. Dress too light, you freeze; wear too much, and you end up carrying layers for half your run. Lululemon (yes, they make men's clothing) may have solved this problem with the new slim-fitting Core Half-Zip. Constructed of their heat-retaining "Rulu" fabric, it kept testers warm in 20-degree weather, even against a lashing bayside wind. And unlike fleeces or zip-up jackets, the nylon-blend material breathes, while underarm vents allow cool air to circulate. The end result: a consistent, comfortable body temperature. [$108; lululemon.com]