Hardened stainless steel neck bushing by L.E. Wilson with a .331" diameter, designed for precise neck sizing in .001” increments with a .003” taper.
Reversible bushing for emergency use or fine-tuning; marked side facing down achieves tighter sizing if brass becomes too springy or for less “squeeze” than the next smaller size.
Compatible only with L.E. Wilson dies, not interchangeable with Forster or RCBS dies; select size by subtracting .002"-.003" from the loaded cartridge's outside neck diameter or calculate using case neck wall thickness and bullet diameter.