8 Gram CO2 cartridges are only compatible with the Byrna HD and Byrna SD. Not compatible with the Byrna SDXL or HDXL or launchers with Byrna boost installed. Byrna's box of ten 8g CO2Â cartridges are custom fit for the Byrna SD and HD Launchers. Now including 1 CO2Â with oil for simple maintenance every 10 CO2Â cartridges used. Each will be good for 15-20 rounds, 4 mags in a 5 round magazine, at full speed. Punctured cartridges within the Byrna HD will leak over time. It is recommended to swap out punctured CO2Â cartridges and leave an un-punctured inside the Byrna HD to avoid any compressed air loss. The Byrna HD will puncture and fire the first round at the same time.