Among the commonly used materials of men's underwear, cotton and fiber materials with good air permeability are usually considered as cooler and more breathable choices. Cotton material has good hygroscopicity and breathability, which helps to dissipate heat and keep skin dry. In addition, other natural fibers, such as flax and bamboo fiber, have similar breathability. However, some synthetic fiber materials, such as nylon, polyester, etc., although absorbing moisture, their air permeability may be slightly worse than that of natural fibers. Generally speaking, it is a good choice to choose cotton or natural fiber products for men's underwear who pursue coolness and breathability.