Technology: ColdGear is a technology that warms the body by printing ceramics on the fabric that store and reflect far-infrared rays. Usage: This is a cold-weather inner shirt suitable for winter training and sports such as soccer. The details of the Under Armour men's compression shirt (model number MCM1297) size SM are as follows: Size Height Chest Waist SM 162-168cm 85-91cm 71-77cm This product is a compression type (a snug fit), so the size feeling is different from that of a general T-shirt. Thank you for viewing.