The Xtenex X 300 series elastic laces fit ANY shoe that has an eyelet size of approximately 3 to 4 mm. They are a perfect choice for most activities involving normal foot movement; from everyday wear to running. These elastic laces are a favorite in athletic shoes, hybrid golf shoes, casual shoes, senior shoes, children's shoes and ANY shoe type imaginable. With three (3) lengths to choose from, you can find the best elastic lace for your shoes by counting your eyelet pairs. The X 300 is the flagship product of the Xtenex Lace lineup. These were the laces worn by Jan Frodeno (Gold Medalist) and Simon Whitfield (Silver Medalist) during the 2008 Olympic Triathlon in Beijing, China.