In fact, underwear belongs to elastic cotton, but cotton is filled with modal and lycra ingredients. Modal is thin, but it's very cold to wear next to your body, so it's best not to wear modal underwear in winter, or you'll feel cold. Lycra is smoother and more cotton than modal, and it is also very close-fitting and fashionable than pure cotton. Pure cotton has plain weave and rib, which has good sweat absorption and is more comfortable to wear. Stretch cotton has better elasticity, but its knitting method is different. In short, it is more comfortable to wear pure cotton.