SPRI Xertubes provide an easily portable, highly versatile way to add resistance training to your workout. Constructed of durable rubber with secure plastic and webbing handles, the Xertubes are suitable for a variety of toning exercises, body types, and fitness levels. Each Xertube is color coded to a specific resistence level, so you get the workout that best suits you. SPRI also includes a strap that lets you safely secure the tube to a door for additional target activities. The kit comes with two illustrated charts of exercises, including bicep curls, shoulder presses, and back extensions. Designed for light and speedy mobility, the strap can be rolled up to stash in a gym bag, suitcase, or overnight grip.