Artificial stone and substitute for ara-to. First stone of the groundwork and used before binsui-do. Kongo-do is used when the sword is rusted or has a flaw. Kongo-do Tokkyu-hin is used by many professional polishers as it can whet very quickly and efficiently. The particle size is uniform, so you you can polish the blade uniformly. Dimensions 21 x 5 x 7.5 cm, weight 1.6 kg.