Promising review: "Long story short (for those with limited time to read my full review,) these are some of the best thermal underwear you can possibly buy. At ANY price. I am a 6' tall, 240 lb. man and the size SMALL fit me like a glove! Which is exactly what you want when buying long johns. You want them to fit fairly tight so they won't be too bulky to wear under your jeans (or other style of pants). These fit like a (comfortable) second skin. I absolutely LOVE them.
Having said all that, let me tell you where I live, and the conditions that I've been wearing these in. I live in Marquette County, Michigan. We've been getting down below zero, with wind chill factors of around 30 to 40 BELOW ZERO. I have yet to feel the need to wear my snowsuit while wearing these! They've been PERFECT for shoveling snow, checking the mail, etc.
Yes, if I were planning on being outdoors for great periods of time, I would absolutely wear these in conjunction with my snowsuit, but for periods of 10-15 minutes, they're GREAT. I can't possibly say enough nice things about these. I bought two pair, but will definitely be ordering more as soon as possible." —YooperCoupleInMarquette
Get it from Amazon for $11.04+ (available in four colors, and sizes S–XXL).