The innovation is the result of a collaboration of the U.S. Department of Energy Office of Advanced Automotive Technology, Daimler-Chrysler, Siemens Automotive, and Johns Hopkins University's Applied Physics Laboratory. The pressure cells inside the fiberglass storage tank are lined with a gas-impermeable HDPE thermoplastic and wrapped in a hybrid mix of high-strength carbon and tough glass filaments wound with an epoxy resin. The cylinders are laid into a "foam egg crate" to absorb impacts. The tank can be made flat, in the shape of a conventional gasoline tank, yet the fuel can still be stored at 25 MPa (3600 psi).