1, height: the height of men is usually between 160 cm and 190 cm, so the size of thermal underwear will be classified according to different heights. For example, code S is suitable for men with height from 160cm to 165cm, code M is suitable for men with height from 165cm to 170cm, code L is suitable for men with height from 170cm to 175cm, and code XL is suitable for men with height.

2. Weight: Men usually weigh between 50 kg and 90 kg, so the size of thermal underwear will be classified according to their weight. For example, size S is suitable for men of 50 to 60 kilograms, size M is suitable for men of 60 to 70 kilograms, size L is suitable for men of 70 to 80 kilograms, and size XL is suitable for men of 80 to 90 kilograms.