The Srixon UR-X features the thinnest thermoplastic urethane cover in the world surrounding the largest core of any golf ball in the industry. The poly-amide enhanced urethane cover provides the feel, spin and control today’s top golfers demand. The solid rubber mid-layer and rubber core combine to give the UR-X the highest rubber content of any golf ball ever played on tour.In fact, 96% of the UR-X is composed of rubber. And rubber is the material that gives a ball its velocity and distance.Think of it another way – the core is the engine of the golf ball – it is the part of the ball that is primarily responsible for distance. Rubber is the material that allows this to happen. So in a sense, think of rubber as horsepower. The more you have, the faster you go.