MAS BT Shank BT30 / BT40 / BT50 Designed to accept milling cutters and, boring, counterboring, tapping and reaming tools, these tool holders are pulled in the milling spindle with help of additional pull stud, which we are also able to provide. ISO Shank 30 / 40 / 50 Designed to accept milling cutters and, boring, counterboring, tapping and reaming tools. R8 Shank Designed to accept milling cutters and, boring, counterboring, tapping and reaming tools. MT Shank Designed to accept milling cutters and, boring, counterboring, tapping and reaming tools.