Cimarron Composites (Huntsville AL, US) has been granted DOT certification for a 47″ diameter type 4 (polymer-lined) vessel for the containment of 4,000 psi natural gas. This pressure vessel is also capable for hydrogen transport. A 30″ diameter, 40′ long variation of this vessel is currently under development, intended to operate at 3,625 psi. Additionally, Cimarron Composites now has DOT approval for a type 3 carbon fiber over-wrapped pressure vessels (COPVs). The 20 liter and 30 liter versions of this vessel are qualified under ISO 11119-3. Though originally designed for breathing air, the COPV can also be used to hold other gasses such as hydrogen. Cimarron also produces a 5,500 psi type 3 helium vessel for rocket launch systems.