The Flex Nomex® Undershirt is a revolutionary advancement in racing underwear, setting new standards for comfort, protection, and performance. Meticulously crafted from a premium blend of 50% Nomex and 50% cutting-edge viscose fibers, this innovative material composition provides unmatched flame resistance and exceptional protection against heat transfer. Designed and rigorously tested by elite professionals in NASCAR, Rally Cross, and WEC, K1 Flex Tech Layers have swiftly become the preferred choice across all motorsports. Prioritizing safety, the Flex Undershirt not only meets but exceeds the stringent SFI 3.3/5 standards. It is engineered for ultimate comfort, featuring an ultra-lightweight 180 g/m² material that keeps you cool, dry, and focused, while also providing thermal insulation to combat heat stress. Experience unparalleled comfort with minimal flat-stitched seams, reinforced with specialized flame-resistant thread. A special non-chemical dry treatment promotes cooling and combats odor, ensuring you stay fresh.