BYRNA 88 GRAM CO2 TWO PACK MISSION 488 GRAM CO2 CARTRIDGES ARE ONLY COMPATIBLE WITH THE BYRNA MISSION 4 RIFLE. Our box of two 88g CO2 cartridges are a perfect fit for the Byrna Mission 4. Each cartridge (new) will be good for approximately 60 rounds (or 3x Mission 4 19 round magazines) at full speed. Punctured cartridges within the Mission 4 CO2 buttstock will leak over time. It is recommended to swap out punctured CO2 cartridges and leave an un punctured cartridge inside the Mission 4