EDIT: High Pressure Air, Nitrogen, Compressed Air, HPA, IS ALL THE SAME!! You're either using CO2, or your using compressed air. Compressed air is the same as high pressure air, nitrogen system, HPA, etc The air you breath is about 78% Nitrogen, 20% Oxygen, 2% CO2 or misc. So many people call compressed air Nitrogen because it's mostly nitrogen. This video I talk about why you should upgrade from CO2 ASAP, regardless of what type of gun you use. You can purchase a PMI Pure Energy 483000 tank for around $50, and it SMOKES a CO2 tank HPA can be used on ALL guns, ALL guns, including spyders, tippmanns, and you'll be shocked how much better the guns shoot. Also, unless you own an Angel, get the high pressure tanks. WAIT! Do you own an Angel? Then get a high pressure 850psi tank Enjoy!