COOLMAX® is a trademarked series of polyester (synthetic) fibers developed for moisture-management and enhanced comfort. The fibers are engineered with a non-round cross-section that increases surface area and enhances capillary action to push moisture from the skin to the outside of the fabric. Coolmax is primarily made from specially engineered polyester fibers (Polyethylene Terephthalate or PET). Its revolutionary performance comes from the unique structure of these fibers: Multi-Channel Fiber: Unlike regular, round fibers, Coolmax fibers are designed with a non-round cross-section, typically featuring four to six channels (or grooves) running lengthwise. Capillary Action: These channels significantly increase the surface area of the fabric (by an estimated 20% compared to round fibers). This unique shape utilizes capillary action to draw (or "wick") moisture (sweat) away from the skin and quickly move it to the fabric's outer surface. Rapid Evaporation: Once the moisture is spread across the outer surface, the increased surface area allows the sweat to evaporate far more quickly than it would with natural materials like cotton. Coolmax 100%: 160gsm