This line of ER mini-nut holders is designed for applications where clearance is a consideration. Nut diameters range from 0.63" to 1.02" (16 to 28 mm) to permit machining where standard ER nuts cannot fit. ER11, ER16 and ER20 sizes are available for CAT40, CAT50, BT30 and BT40 spindles. The mini-nut holders are manufactured to extend perishable cutting tool life and improve CNC machine performance, the company says, noting that each taper is precision ground to exceed AT3 industry standards. Maximum TIR (runout measured from the outside of taper to the inside of collet pocket) is said to be 0.0001". The holders are factory balanced to 18,000 rpm at G2.5.