Designed to facilitate the exercises of the Franklin Method. Balls are the ideal density and size for relaxation exercises of the neck, jaw, elbow, hip and more. * Approximately 10 cm in diameter. Set of 2. * Franklin Balls come inflated but to adjust firmness a needle pump is needed. Sold separately. * *People with known sensitivities may want to consider using the (orange) Smooth Franklin Ball SetÊwhen performing the Franklin Method exercises.