If you have ever done a one on one session with me the chances are you would of laid on these BakBalls in order to mobilize the thoracic area of your spine. I always advise that my personal clients get themselves two tennis balls in a sock as a cheap alternative. However, they are cheap as chips on this site at $39! I bought mine from another health practitioner that marked up to $70 for a pair… sucked in! Black ones are a lil firmer, you can get the red ones that are softer. I cannot emphasize how good these products are for your overall posture. They are great for getting to the bits a foam roller cannot. To all of my one on one clients… get to it!