Centaur Precision Tools ER Rigid Tap Collets can be utilized for synchronous tapping operations using any ER collet chuck. The collet bore is exact tool diameter, with square drive, for accuracy and rigidity. All Centaur ER rigid tap collets are manufactured from high-grade spring steel, hardened and ground with 100% quality inspection.Centaur Precision ER Rigid Tap Collets conform to DIN6499A.