Redi-Thotics ULTRA orthotic offers rigid arch support to those with flat, flexible feet or Hallux Rigidus. The ultra-thin Rylon shell will support and cradle the arch while the extra deep heel cup locks the rear foot in place for stability. A neutral post on the rear foot makes adjustments with peel and stick rear foot posts quick and easy. away moisture while maintaining a soft upper for extra comfort and dryness.