Nidec-Shimpo 2-Litre Milling Jar (With Alumina Ball Media)Shimpo Ball mill jars are of the highest quality. Each impurity free porcelain jar has two wing nuts to close the lid with a rubber seal. Included with the jars is the correct quantity of alumina balls. The ball sizes are different so ensure efficient and rapid grinding of hard material. NB: These are hand thrown and finished jars of very high production quality, Still made by a small production pottery in Japan.