Carmex Single Long Carbide Shank Threading Insert holders - For Carbide External/Internal Threading Inserts - SR0021K21CMeet the Carmex SR0021K21C Single Long Carbide Shank Threading Insert Holder a precise, long reach solution for external and internal threading on CNC mills. Built for shops tackling deep or extended overhang threading, this holder combines rigid support with efficient coolant delivery to boost productivity. Internal coolant bore: Directs coolant to the cutting edge for improved chip control and insert life. Long reach up to 270 mm 10. 5 in: Supports