ER20 Collet & Drill Chuck With JT33 Sleeve & Hex Nut ~ Maximum RPM is 8,000. ~ T.I.R. is <= .0002″. ~ Superior Finish. ~ Precision ground & hardened for accuracy and precision. ~ ER collet sleeves provide rigid & accurate holding of ID tooling. ~ These collet sleeves feature ground shanks and tapers. ~ They are compatible with standard Jacobs taper spindles. ~ They can be used for coolant-thru applications. ~ Superior to keyed and keyless drill chucks in concentricity and holding power.