10 Best Thermal Underwear Sets 2026 in the United States

The Merino.tech Merino Wool Base Layer Men’s Set is made from 100% superfine 17.5 micron merino wool, a top-quality material known for being soft and comfortable without causing itchiness. This set comes in different weights, with the midweight version at 250 g/m² offering a good balance of warmth without overheating, making it suitable for cooler conditions or active outdoor use. It includes both a top and long john bottoms, plus a bonus pair of merino wool hiking socks, which adds value.

The natural moisture-wicking ability of merino wool helps keep you dry by pulling sweat away from your skin, and its odor-resistant properties allow for extended wear without developing smells. The fit is designed for comfort with no rubbing or bunching, important for base layers worn close to the skin. Additionally, the fabric breathes well, aiding in body temperature regulation so it can be worn across different seasons.

This set requires gentle care—hand washing and air drying are recommended to maintain durability and shape, which might be less convenient than machine washing. Imported and offered with a gift-quality presentation, the Merino.tech set provides quality and performance, making it a solid choice for men needing reliable thermal underwear for hiking, winter sports, or everyday cold weather comfort.

The Cuddl Duds Thermal Underwear set is designed to keep you warm and comfortable in cold weather, thanks to its cozy fleece lining and heavyweight feel. Made from 93% polyester and 7% spandex, it offers a good stretch that moves with you, making it comfortable for active wear or lounging. The moisture-wicking fabric helps keep sweat away from your skin, which is great for staying dry and warm during physical activities. Plus, it offers built-in UV protection with a rating of 50+, which is a nice bonus if you plan to wear it outdoors. The fit is modern and close to the body without being bulky, featuring details like thumbholes in the sleeves and a higher rise in the leggings for added comfort and coverage.

The product is machine washable and lightweight at about 15 ounces. Durability is generally solid given the dense knit fabric, but as with many polyester blends, it may pill over time with heavy use. This set is well suited for women looking for a warm, stretchy base layer that can double as casual wear in cold seasons.

The Merino.tech Merino Wool Base Layer Set is a strong choice for anyone looking for quality thermal underwear that works well in various weather conditions. Made from 100% superfine 17.5 micron merino wool, this set offers excellent softness and comfort without the itchiness often associated with wool. The midweight fabric (250 g/m²) strikes a good balance—not too bulky but warm enough for cold conditions. Fit is described as comfortable for daily wear, designed to avoid bunching or overheating.

One of the standout features is its natural moisture-wicking ability, which helps keep sweat away from your skin, making it feel dry and fresh during activity. Alongside that, the fabric resists odors naturally, so you can wear it longer without worrying about smell. The set includes both top and bottom pieces plus a merino wool beanie, adding good value and versatility for outdoor use or layering.

Care-wise, the recommendation to hand wash and lay flat to dry might be less convenient for some, though the fabric is durable if cared for properly. Machine washing is noted as possible, but the gentler method will help maintain longevity. Since the product is imported and specialized, it may carry a higher price point, but the brand backs its quality with a satisfaction promise. This thermal underwear set suits men seeking comfortable, breathable, and naturally temperature-regulating base layers for winter sports, outdoor work, or everyday cold weather wear. If you want something soft, odor-resistant, and effective at moisture management, this set delivers well. However, if you prefer easy machine washing and don’t want to handle delicate care, you might want to consider alternatives.