The most common gas propellant is CO2 and typically comes in the three sizes of 9 oz, 12 oz and the 20 oz. The bigger 20 oz tanks can fire 500 to 1500 shots depending on the efficiency of the marker. Due to its low cost production, the CO2 propellant is of lower quality compared to compressed air. CO2 also sometimes malfunctions when the outside temperature goes lower than 40 degrees Fahrenheit while compressed air can withstand much more temperature change. You should not use CO2 in higher quality markers which would be any gun with an electronic board (besides the Vibe).

Compressed air tanks will come in 3000 and 4500psi variations which can be anywhere from 45ci to 92ci. The 3000 psi tanks can fire anywhere from 500 to 1500 depending on the gun and 4500 psi tanks can fire anywhere from 1000 to 3000 depending on your marker. Compressed air will also give more consistency and accuracy.