The Aircast Replacement Sock Liner is intended to help reduce skin irritation while wearing an foot brace or walking boot. It's compatible with the following Aircast Walker Braces / Walking Boots: XP, FP and SP models. This full length, stretch tube sock measures 22 inches long. Available in white, this closed-toe sock is made with a cotton/polyester/lycra spandex blend. One size fits all.