ItemProductSurface hardnessCore hardness 1High chrome cast grinding media Hrc 58-65More than hrc 55 2Low chrome cast grinding media Hrc 48-55More than hrc 46 3Medium chrome cast grinding mediaHrc 50-60More than hrc 48 4B2 forged grinding mediaHrc 58-65More than hrc 55 5B3 forged grinding mediaHrc 58-65More than hrc 55 6Bu forged grinding mediaHrc 58-65More than hrc 55