Mount: 1/2"-20 UNF (electric hand drill)
Auxiliary functions: It MUST contain retaining/lock ring (plastic red ring in the attached picture).
Accuracy/concentricity/axiality: Better or equivalent to 0.1 mm.
Jaws: Hardened or may have carbide inserts.
Auxiliary mounting options: Inner axial hole, LH thread, for screw is preferable, but not strictly necessary
Shipping method: Doesn't matter.