These are the wraps that use air compression to improve circulation, soothe sore muscles, and reduce swelling in the calves. Built-in airbags wrap around the lower legs and inflate and deflate to three zonal air pressures (30-90 mm Hg at top of wrap, 40-100mm Hg in the middle, and 50-110mm Hg at bottom). Similar to hospital compression boots, the wraps use compression intervals to stimulate circulation and help facilitate blood flow back to the heart. The wraps are also useful for recovery after running or exercise. Adjustable hook-and-loop closures fit calves up to 12 1/2" at bottom and up to 18" at top. Charges via USB.