These spring collets are made of high quality 65Mn spring steel for CNC milling lathe tool and work-holding engraving machine. There are total 10 collets of various sizes in on set which can basic meet your need. Collet must be placed into collet chuck nut before inserting into collet chuck. <br /> <br /> <b>Specifications:</b><br /> Material: 65Mn spring steel <br /> Model: ER20 <br /> Height: 30mm <br /> OD: 15mm <br /> Run-Out Tolerance: <0.008mm <br /> Range: 3mm, 1/8", 4mm, 5mm, 6mm, 1/4", 8mm, 10mm, 12mm, 1/2" <br /> <br /> <b>Package Included: </b><br /> 10 x ER20 Collets <br /> <br />