≪Certified by NPO Japan G-Ball Association≫ ≪Certified by Japan Society of Gymnastics≫ ✅ Material: Non-phthalate vinyl chloride ✅ Size: Diameter 8cm, 2 balls per bag ✅ Brand: GYMNIC ✅ Model Name: LP9755 ✅ Color: Green ✅ Material: Hard rubber ✅ Usage: Used for massage and relaxation ✅ Quantity: Set of 2 These are spiky balls of a comfortable size. Rolling these balls on the body, or stimulating the soles of the feet, palms, and various parts of the body feels good. The massage effect promotes blood flow, and provides tactile stimulation. Reflex Ball 8cm, 2 balls per bag, comes with a booklet explaining how to use them.