Black Mountain Products deep tissue massage ball is designed with large spikes for effectively massaging muscle tissue. Massage balls are the perfect exercise tool for relieving muscles soreness, pain, stiffness, and recovery. With a small design each ball is excellent for massaging legs, shoulders, feet, back, hips, and glutes. With a 3.5 inch diameter, massage balls are great for traveling, office use, and storing. Ideal for massage therapy to efficiently improve movement and increasing flexibility. Each Black Mountain Products Massage Ball comes with a lifetime manufactures warranty.