3.175mm Stainless steel ball aisi 420 440 1)100% original 2)High hardness 3)good ... SteelProduct Name: stainless steel ballMaterial: AISI304,316,316L,420,440,200,202MDiameter: 3.175mmGrade: G10-G1000Certificate: ISO9001:2008 SGS ... several types of stainless steel balls, ranging from the 440 type which offers the greatest hardness and surface finish ... reputation. 3.175mm Stainless steel ball aisi 420 440