Back Pain Relieving Wheels fit perfectly between your shoulder blades, targeting the muscles that go up and down your spine. Simply lay back to elongate your spine and roll away pain. This set includes 3 wheel sizes (6”, 10” and 12”) to go from the least intense massage (large wheel) to the deepest massage (small wheel). The built-in “spinal canal” allows for increased muscle massage. Just 5 minutes a day relieves pain and muscle fatigue. Includes 3 wheels.