OPTP offers four balls to accomodate various body areas. Inflate or deflate balls as needed to adjust size or firmness.
The Beginner Ball is soft and used for beginners, those with osteoporosis, arthritis or limited flexibility. 21cm or 8.25" in size.
The Intermediate Ball is firm and smaller for detail work; especially the shoulder, neck, abdomen, pelvis and arm. 17cm or 6.6" in size.
The Advance Ball is the firmest and is used for spinal work or specific muscle release. 18cm or 7.25" in size.
Balls are shipped partially deflated. A needle inflation pump (#58613) is sold separately.