1,DURABLE MATERIAL: Collet chuck holder is made of excellent manganese steel material, surface quenching black treatment, possess strong oxidation resistance, high hardness, long service life 2,APPLICABLE SIZE: CNC milling extension rod is suitable for ER16A chuck, easy to install, even if you are a novice can be easily removed for convenience 3,INCREASED EFFICIENCY: Milling machine chuck holder has straight shank, clamp nut, are the machining products that make your work better, more efficient and more durable 4,PERFECT REPLACEMENT: The ER16A chuck is a good replacement for older parts and can be used in CNC milling machines, useful and practical 5,WITH BOX: Collet chuck tool holder equipped with a storage box for easy storage, portability and access, and also prevent damage and loss, also with a wrench