The Foil Monofin teaches the Full Body Motion developed and made popular by Coach Bob Gillett. The Full Body Motion utilizes the entire body to create a powerful and undulating dolphin kick through the water. The Foil Monofin promotes an equal use of up and down kicks for propulsion throughout the entire dolphin kick movement, increasing core and leg strength. Natural rubber provides a secure and comfortable fit. Sizes xs 35-37 s 38-40 M 41-43 L 44-46