The Hyper Impact Therapy Spheres help relieve sore and stiff muscles using a targeted tissue and acupressure system. The power strap expands and targets hard-to-reach areas such as the upper/lower back, legs, and feet. Great for pre and post-workout recovery! The spheres charge using the USB cord. Each ball is turned on using the power switch and can be adjusted to 3 different speed modes. Includes massage instructions for neck roll, back roll, foot rejuvenation, wrist relief, and more! Set includes 2 therapy spheres, 1 power strap, and 1 USB charging cable. with a peekaboo cutout and instructions for use. Hy-Impact 3 Speed Vibrating Massage Therapy Spheres with Expandable Strap,