Yingfa resistance stretch cord allows athletes to mimic the movements they make in the water, an excellent way to build up critical shoulder and back muscles. Which Cord Size To Buy Diameter / Length Recommended 11mm / 3m Kids below 12 years of age 11mm / 4m Kids below 12 years of age, general swimmers 11mm / 5m Profesional swimmers 13mm / 3m Kids above 12 years of age, adults 13mm / 4m Kids above 12 years of age, adults, general swimmers 13mm / 5m Profesional swimmers Simulates swimming movements out of the water and isolates vital muscle groups Builds strength and endurance Trains triceps, chest, biceps, shoulders and abs Improves flexibility and range of motion for all four swim strokes Builds specific muscle strength to prevent or combat injury Small and lightweight cords for easy travel Material: Cord (Silicon), Soft Handle (Foam), Hard Handle (Plastic) Note: Due to the difference between different monitors, the picture may not reflect the actual color of the item.
