... balls have 5 kinds of different firmness. They are soft, mid-soft, medium, mid-firm, and firm. For new equipment ... , soft and mid-soft balls are the best choice. For equipments in routine process ... (3 inch) soft ,hard ,medium softOD95mmDN100 (4 inch) soft ,hard ,medium softOD124mm DN125(5 inch) soft ,hard ,medium softOD150mm DN150(6 inch) soft ,hard ,medium ...