RaceQuip SFI 3.3 rated socks are knit from a blend of aramid and FRC fabrics to achieve a comfortable fire retardant garment. The properties of this unique fabric structure create a lightweight fabric that performs like Nomex yet is much more cost effective. The Fire Retardant Cotton (FRC) component of the fabric promotes a soft and supple lightweight feel. Since its hypoallergenic, it wont irritate your skin like some other materials tend to do. This proprietary fabric blend is also superior at wicking away mositure from the skin and dries quickly. All RaceQuip fire retardant underwear garments are machine washable and retain their shape well. Exceeds SFI 3.3 rating and available in black sizes Small - 2XL - remember that racing underwear is designd and built to fit snugly.