Recommended series: NTS 250, Merino 150
 
Smartwool is a major producer of merino wool outdoor products, most well-known for wool socks, accounting for more than half of the North American share, and has been used by USSA (Ski and Snowboard Association) athletes since 1998 and was featured at the 2010 Winter Olympics. Its wool pressure running socks also won the 2011 Asian Outdoor Industry Award. In addition to the familiar wool socks, Smartwool's thermal underwear is also excellent, with its Merino 150 collection being named "Best Women's Thermal Lingerie" by The New York Times Wirecutter in 2017.
 
Outdoor thermal underwear is usually classified as lightweight, medium-heavy, and expeditionary heavyweight based on weight (in g/m2). Smartwool NTS 250 is a medium-heavy thermal underwear with a moderate thickness. In addition to the round neck, there are also zippered and hooded models, which can be worn in autumn and winter, and are practical.
 
Although new fabrics are constantly being developed, the truly high-quality insulation is still made from animals. NTS 250 is made from 100% merino wool, a fibre that acts as a natural thermoregulator and keeps you dry and warm even when worn close to the body in wet weather. The average diameter of merino wool is only 19 microns, which makes NTS 250 soft to the touch, and the significant antimicrobial properties of the wool make NTS 250 deodorant. The wool fabric of NTS 250 is further treated with a SPF of 50 and is machine washable. However, it also has the shortcomings of insufficient durability and relatively slow drying speed, and the domestic price is more than 1,000 yuan.
 
The Merino 150 is Smartwool's thinnest and most recommended collection. Launched in the fall of 2017 and weighing only 170g, it is a knitting modification that continues the advantages of NTS 250, using a double layer of "core-spun yarn" for sewing, combining 87% merino wool with 13% nylon for much improved durability. In addition, the seamless design of the Smartwool shoulders allows for more stretch and prevents friction with the backpack straps. The domestic price of Merino 150 is around 800-1000 yuan, which is lower than NTS 250.
 
The price of Smartwool thermal underwear is higher in China, almost twice that of foreign countries, and there are large differences between e-commerce channels, so it is recommended to shop overseas through reliable channels.