Purchased on Amazon for ¥1636. I accidentally bought two, so I'm selling this one. I use it regularly for abdominal muscle training. <Product Description> The secret lies in the single tooth on the sole. Core training just by standing: "Sole Balance Colon." "While-doing training" allows you to do core training at home, using geta (traditional Japanese footwear) that professional athletes practice. Just by standing on the single tooth of the sole, you can target deep muscles and improve core strength. Suitable size: 22.5~25.0 (cm), Weight: 420g Material: Fabric: Polyester, rayon, etc. Filling/Sole: Polyethylene