NitroAir is the first pre-filled cartridge loaded with compressed nitrogen gas for use with N2-designated air rifle. Umarex's NitroAir is the most revolutionary, innovative, and convenient solution for high pressure air rifles. Compressed to 3,600 psi this two-pack has 32 grams of nitrogen (N2) in each cartridge and works seamlessly with the Umarex Komplete NCR, the very first N2 cartridge PCP air rifle. These revolutionary nitrogen cartridges should only be used with air rifles that are designated by a N2 symbol indicating the air rifle is for use with the pre-filled, disposable nitrogen cartridge. NitroAir cartridges are not for use with CO2 air rifles. CO2 powered air rifles are designed for a much lower operating pressure. To prevent the use of Umarex NitroAir cartridges in a CO2 powered air rifle the patent-pending piercing surface is inset to prevent such use. When installing, screw the cartridge into the N2 designated air rifle. Once it is pierced it may become difficult to turn the cartridge but go ahead and turn it a half turn further if possible to ensure a good seal. Unlike CO2 powered rifles, there's no need to remove the NitroAir cartridge from the rifle for storage. Just make sure to keep your air rifle unloaded and locked up to prevent unauthorized use. When it is time to replace a cartridge be sure to use the air bleeding mechanism on the air rifle to drain all the air before attempting to remove it. Lastly, when the cartridge is empty, it's made of steel so you can recycle it where steel is accepted. Nitrogen makes up 78% of the Earth's atmosphere and is a non-toxic, stable gas but you should always read and understand the warnings and cautions that come with NitroAir cartridges and the owner's manual that comes with any air rifle that uses them. NitroAir can be used with N2 designated air rifles in both hot and cold temperatures. This is a benefit that CO2 does not offer and NitroAir means you don't need an expense air compressor or an air rifle hand pump that results in a sweaty workout just to get some trigger time. Stock up on NitroAir cartridges. Keep them in a cool, dry location and they'll be ready for use many, many years down the road making them an excellent source of high pressure air for prepping and survival persons looking to power their PCP air rifles for hunting to putting food on the table.