The M4 Tank Adapter allows you to screw in a co2 or HPA tank directly into the bottom of the grip. The advantage to using a co2 or HPA tank is the incredible number of shots you’ll get. Most players can shot all day without refilling. It’s the most economical way to play.
Shots per source: (actual results may vary due to atmospheric conditions, tests performed at 72°F)
9 oz Co2 = 1700 shots
12 oz Co2 = 2280 shots
20 oz Co2 = 3800 shots
68 cu in HPA @ 4500 psi = 4400 shots
48 cu in HPA @ 3000 psi = 1920 shots