How to choose warm underwear big analytical skills

The cold winter arrived, facing the market of many brands warm underwear, how to choose and buy a performance, the price is more appropriate to keep warm underwear become a concern of many people
See fabrics:
An underwear inside and outside the stand or fall of fabric, the influence is the key whether comfortable to wear. Currently on the market to keep warm underwear according to the high, medium and low-grade three categories to points, the use of the fabric have 40 a cotton, 32 clubs cotton, polyester-cotton (cotton content at 30% ~ 40%), pure chemical fiber and so on many kinds of, among them with internal and external surface all use 40 more than a cotton products for optimal, its softness and fineness, permeability, glossiness, are preferable, and after washing won't rise cottony ball, long-term wearing also won't have clothing broken wires, wo phenomenon.
By hands:
High quality underwear in the middle of the thermal insulation layer use superfine fibber (diameter in 1.2 within silk) weaving, garment is soft and comfortable and have good warm performance, with the hand kneading, feel soft, and no foreign body sensation. Summary of the composite technique, intermediate and advanced, garment surface and intermediate one feels strong, dress function also better.