The Cool Knit® Crew is designed specifically to aggressively wick sweat away from your skin, keep you cool, and prevent saturation so that you can perform. The proprietary Cool Knit® fabric features DuPont™ Kevlar® and Nomex® brand fiber - the first flame-resistant fiber selected for use in military uniforms, which makes a lightweight garment with a four-way stretch for a trim fit that keeps its shape over time, and is highly compressible so that you can bring it anywhere. Safe-to-Fly (StF) Approved by U.S. Air Force - Air National Guard.