Product details:

The StretchCordz Long Belt Slider was improved for safety and comfort. Used for adding resistance to swimming, the Long Belt Slider is s #1 in-water resistance product. It provides swim out and pull-back resistance to improve strength and stamina. Accelerate quicker, strengthen the finishes of each stroke, and improve your times. A proprietary, embedded safety cord runs the full length of the tubing and acts as a limiter to help prevent over-stretching.