Very required tool that allows you to pull a broken case out of the chamber of your rifle. A cartridge case rim can be pulled off by your rifle's extractor, and your rifle becomes a club. In the field you cannot get the stuck case out of the chamber. The broken shell extractor fits inside the stuck case and pulls it out from the neck, using the force of the extractor. Very clever and required, broken shells are somewhat rare, but one renders your rifle worthless.
This works for all 8mm rifles.