It suits for all tool holder with ER40UM nut with M50 1.5 thread. - These ER40 UM Bearing Collet Nuts won't improve your machines accuracy much (maybe. 0002") but they will extend your tool life. - These bearing nuts float the collet in the center of the tool holder and as they are tightened, they won't spin the collet and therefore they don't scratch the tool holder, spindle cone or the collet.
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