The incredible Reebok Men's Carcharodon Top is a smooth, seamless running shirt with embedded silver fibers in the core, back neck, and lower back. These fibers respond to temperature changes and keep you cool when it's hot and warm when it's cool. Made of 100% polyester and 86% PES/9% EL/5% X-Static® PlayFresh thermodynamic silver embedded fibers. Imported.