Adjustable ER Nut - Absolute Zero Nut
You can now dial in your part or cutter to "zero" it out. After you get your new ER nut, just chuck your part or cutter, place an indicator on it to locate "out of round" and adjust as the needed set screw(s) to zero out. It's that easy. Your parts can are now super accurate and you mill cutters can last longer with better accuracy!