延长杆用优质弹簧钢制造。热处理硬度48-53HRC,外圆内孔经精密研磨，同心度达0.005mm，一般可配ER11,ER16,ER20夹头。用于数控铣加工中心，模具雕刻，具有深加工小孔径精度高等特点，可减少对加长刀具的使用，降低成本，提高效率。具体规格如下：C16-ER11A-120L  ,C16-ER11M-50L,  C16-ER11M-100L,  C16-ER11M-120L,  C16-ER16A-50L,   C16-ER16A-00L,  C16-ER16A-150L,  C16-ER16M-80L,  C20-ER16A-100L,  C20-ER16A-150L,  C20 -ER16M-80L,  C20-ER16M-100L,   C20-ER16M-150L ,  C20-ER20A-60L,  C20-ER20A-120L,   C20-ER20A-150L,   C20-ER20M-60L,   C20-ER20M-100L,  C20-ER20M-120L ,  C20-ER20M-150L.