Marushin G21 Cartridge Set (8mm) A box of 5 cartridges for the Marushin Shell Ejecting Glock 21. If you are seriously considering going skirmishing with your Marushin Glock 21, then you will sure as hell need more of these shells! To be able to use these Shells, you?ll need to have the Marushin 8mm Shell Ejecting Glock 21 [MRS-G21DM]. Product Code MRS-ACC-G21DM Price (USD) $18.50