1.material:IAISI1015 2.Hardness:HRC58-65 3,steel ball grade:G100-G1000 4,good quality & fast delivery Product discriptionSize : 1/4"*7,1/4"*9,3/16"*7,5/32"*9,5/16"*9 or requiredMaterial: Chrome steel & Carbon steelGood qualityFast delivery time Steel ball retainer fore bicycle