Firm and solid, these lightweight, uncrushable balls keep their shape and do not absorb moisture or bacteria, Smooth foam surface, About Therapy Balls: Use the Myo-Release Ball in myofascial release exercises and movements to assist in equalizing muscle tension throughout the body, The different sized balls allow you to treat trigger points based on their size or sensitivity, The larger balls let you spread the force out over the muscle area, and the smaller balls allow you to target only a small part of the muscle and penetrate the tissue more deeply, SKU: PWSS131