Made from soft, comfortable merino wool, these base layers are not only warm, they're durable too. That makes them great for travel, long days on the ski hill, or just lounging around at home. They even come in three different colors for those who want something other than basic black or white. This also has a matching bottom if you are looking for a complete set.If there is an outdoor brand that knows a thing or two about keeping us warm during the winter, it's Helly Hansen. The company has been making cold-weather gear for more than 140 years and its base layers are some of the best in the business. Pair the Lifa crew top with the matching base layer pant and you have a winning combination for any active outdoor winter pursuits. As the name implies, these base layers are built for everyday use, meaning they are just as handy for cold commutes as they are for winter hikes or a weekend on the slopes. Made with a blend of stretch fabrics and merino wool, they're designed for maximum comfort and versatility no matter where you end up wearing them. This also has a matching bottom if you are looking for a complete set.Under Armour's mid-weight base layers include plenty of features for those cold-weather workouts. For instance, the fabrics not only have four-way stretch properties that won't inhibit motion in any way, but they're also designed to avoid collecting odors. Throw in the ability to quickly wick perspiration away from the body, keeping you warmer for extended periods as a result, and you'll quickly find yourself running out of excuses for why you're not exercising in the winter. This also has a matching bottom if you are looking for a complete set.If you're looking for protection from the cold that is easy on the wallet, it's tough to beat base layers from ColdPruf. These tops and bottoms offer excellent performance at a great price, making them a great choice for outdoor enthusiasts on a budget. This also has a matching bottom if you are looking for a complete set.