The Tiger Ball 4.4 Peanut Foam Roller is a revolutionary foam roller great for deep tissue muscle massage. This patent-pending inventive tool offers even, penetrating and controlled deep muscle massage with "Gription" on the muscle and fascia. The signature Tiger Tail "fingerprint" pattern helps it grip to surfaces to keep it from sliding around, helping with sustained traction on the muscle. Two 4.4" balls are designed to cradle the spine while relieving tension in the surrounding muscles. Perfect for the spine and bigger muscle groups, such as hips, hamstrings, glutes, back, neck, and shoulders. The "groove" in the peanut offers perfect spinal spacing so that back massage hits all the muscles and avoids the spine. Lean or lie on the peanut and use your weight to press and massage muscle areas. The ball is surprisingly durable, firm, and lightweight at only 9 ounces. It won?t change shape despite the pressure or body weight. 8" massage surface.