4Pcs/Set Safe Finger Exercise Ball Reusable Delicate Mini Wrist Finger Pressure Intensity Rehabilitation Specifications:You can definitely effectively improve your hand strength with this ball, which can stimulate parts of your hands to release the pressure of life, it will also help you improve your posture when playing the piano. Undoubtedly, you won't feel tired of playing this ball, because of the light texture, and it will be soft to use, providing a comfortable hold, 4 different sizes can make it fit for different hands. This will make the plastic comfortable to use. This ball has 4 different sizes for you to choose from. It is suitable for beginners and learners to improve posture and release finger pressure. Item Name: Finger Exercise Ball Material: Plastic Features: High Elasticity, Soft, Comfortable Size Details:Diameter: 5.5cm/2.17" (Approx.) Diameter: 6.5cm/2.56" (Approx.) Diameter: 7.5cm/2.95" (Approx.) Diameter: 9.5cm/3.74" (Approx.) Notes: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. Package Included:1 Set of Finger Ball Exercise (4 Pieces)