A book introducing a tennis ball diet method to help alleviate lack of exercise. - Title: Tennis Ball Diet - Author: KAORU - Features: Relieves lack of exercise, boosts immunity - Contents: Information on post-exercise cool-down and full-body slimming - Size: Includes a 7.5cm tennis ball I saw a feature on TV about the *Tennis Ball Diet* book and immediately bought it at the bookstore. I bought the tennis ball at a nearby tennis school, thinking that the ones from the 100-yen shop might not be effective! You can start right away when it arrives!! Please refrain from purchasing if you are sensitive to used items. Thank you for viewing.