Highmark Snowpulse Air CylinderThe Snowpulse cylinder is made from aluminum and should be filled with dry compressed air to 3000psi. The cylinder has a pressure gauge so you can see how full it is, or check for the unlikely event that it has leaked. You should always check the pressure gauge before you head out. The extra cylinder is great to have as a back up on a long trip in case you accidentally deploy your pack and you are nowhere near a refilling station. Used for all Mammut