-These ER32UM Bearing Collet Nuts won't improve your machines accuracy much (maybe .0002") but they will extend your tool life.
-Normal collets can get scratched as they are tightened inside the tool holder cone.
-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.
-It suits for all tool holder with ER32UM nut with M40*1.5 thread.