Hardened stainless steel neck bushing from L.E. Wilson, designed for precise neck sizing in .001” increments with a .003” taper for emergency resizing or fine-tuning.
Not interchangeable with Forster or RCBS dies, and to select the correct size, subtract .002"-.003" from the loaded cartridge's outside neck diameter or calculate based on neck wall thickness and bullet diameter.
The .307" bushing size refers to the middle diameter, and inverting the bushing allows for tighter sizing if needed due to hardened brass or for less “squeeze” than the next smaller size.