Redding's Titanium Nitride Neck Bushings are heat treated steel bushings with a Titanium Nitride coating to increase surface hardness and reduce sizing friction.
The bushings come in a range from .185" through .368" in .001" increments, with the size indicated by the last three digits of the part number.
This particular bushing has a diameter of .340 inches, suitable for precision reloading applications within that size range.