Redding Neck Sizer Bushings freely interchange in all Redding Bushing-Style Sizing Dies. They are available in .001"; increments covering all calibers from 17 to 338. By selecting the correct bushing, you are now able to provide just the right amount of neck tension to properly hold the bullet without excessive resizing. All bushings are marked with size identification. To determine proper Bushing size, measure the outside neck diameter of a loaded cartridge with a precision micrometer, then subtract .001"; to .002";, to allow for brass spring back and bullet tension. Shellholder and dies sold separately. Steel bushings are heat treated steel. Redding bushings are hand polished with a surface hardness of Rc 60-62 to reduce sizing effort. Titanium Nitride bushing offer the same features as steel bushings, but also feature titanium nitride to further increase the surface hardness and reduce sizing friction. Dimensions: 1/2"; O.