Product properties: These steel balls are made of AISI52100 chrome steel, assortment of 3/4inch,5/8 inch, 9/16inch, 1/2inch, 7/16inch, 3/8inch, 5/16inch and 1/4inch to meet your basic requirements for coin rings. Product advantages: These balls are highly polished, with high precision and excellent surface finish. Warm note: 1)These small size balls are solid steel, please keep them away from children under 5 years old so as not to cause accidental swallowing.. 2)Although these chromium steel balls have good rust resistance, but it is recommended to use a dry cloth to wipe clean after use and apply a layer of oil, so that they have better rust resistance, to extend their service life.