You can go to Yamuna Zake's website at http://www.bodylogic.com and check out all the different size balls, the book, the video etc. ย In fact, I don't think she will sell you any balls unless you purchase either the book or the video. ย Probably legal reasons...similar endangerment sites for deep tissue massage as with the body rolling (ie: ย over floating ribs etc). ย I bought the book and balls after going to the AMTA convention two years ago. ย She was one of the speakers. ย Unfortunately, I did not attend that workshop, but all my friends did and I soon wanted in on all the fun. ย Honestly, I don't like her writing style. ย A bit self-indulgent...kinda like she's just trying to fill up space to make a thicker book...but the pix are good and it's pretty intuitive stuff anyway. ย I hear the video is better...but if you can go to one of her workshops, do it. ย She is an amazing person. ย I ABSOLUTELY LOVE BODY-ROLLING!! ย I find that I've adapted it a bit for my own body...but just learning to listen to my body, feel it relax into the balls...has been really empowering for me. ย In two minutes of use, I corrected a two year knee problem that hasn't returned since. ย Check it out. ย Definitely.