The inflation system usually consists of a pressurized cylinder, a regulating valve, two high pressure hoses and two aspirators. The cylinder's volume can be between 100 and 1,000 cubic inches (1.6 and 16.4 litres), pressurized to about 3,000 pounds per square inch (200 standard atmospheres) with either gaseous Nitrogen (N2), or a mixture of Carbon Dioxide (CO2) and Nitrogen. Once made of steel, most cylinders now are made of aluminum or alloy cores wrapped with fiberglass, or other lightweight, fuel saving materials.