This is our NF-450 chuck with special hardened top tooling. The chuck has Sub-jaws mounted on it to accept interchangeable inserts. All top tooling is hardened to 58/63 Rockwell “C” and ground to <1/10,000” T.I.R. for maximum durability and repeatability. The inserts mount to the subjaws with (1) screw connection for fast and easy changeover.