The x300 series elastic laces are the leading model in the xtenex range very popular among triathletes for their ability to hold the foot in the shoe and ease of getting on and off in the transition zone xtenex laces are designed so that when the tension is released the lace can not travel back through the eyelet which means the shoe wont slip the knotted design system is designed to address the source of foot related pain discomfort and injury whilst still maintaining performance