Strength is pounds of force needed to bend into U-shape. Portable and convenient exercise, rehab, and injury prevention equipment. Treats tennis & golfer elbow, relieves tendonitis pain, and improves grip strength. Clinically researched and proven to reduce elbow pain by 81% and increase strength in the tendons by 72% in tennis elbow patients. Ridged design is easy to grip and twist for elbow, wrist, forearm, and hand rehabilitation and strengthening, lateral epicondylitis therapy, and great for musicians, painters, and gardeners. The packaging includes detailed exercise instructions.