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. Made in the USA.