The Forster Bushing Bump Neck Sizing Bushing - .336" allows case necks to be sized to your exact requirements in a Bushing Bump Neck Sizing Die. An ultra smooth bushing produces better loaded rounds, so Forster uses a super-cooling cryogenic process. Cryogenically treated steel produces filler particles that refine and close the steel's surface. Bushings are heat treated and honed to the precise inside diameter stated.