Original Item: British WW2 military issue ruptured shell extractor for the British .303-in cartridge. This is known in British nomenclature as a Plug, Clearing, .303-in.

If the head of the cartridge case breaks off, the extractor is slid into the chamber, and the bolt is then allowed to go home. The extractor engages the inside of the broken shell and retracting the bolt pulls it out of the chamber, enabling the gun to resume firing.