Paintball Gun Quick Change 12 Gram Co2 Cartridges Cylinder Adapter is 4.68 inches long and 88g bottle thread.
When you tighten the nut, the needle inside the nut pierces the CO2 Cartridges, and the gas moves from the cartridge to the gun. (slip a 12 gram CO2 cartridge in the rear tube, and tighten. The cartridge is pierced and the CO2 flows into the marker),15-20 shots, when you use it, When replacing to unscrew the nut to remove the CO2 Cartridges for replacement.
This will not take you too much time, and it will be a good home defense.
Note: After use, you will not be able to retain your CO2 throughout the night