English: Seen in 1969, Baseball II was a large version of the baseball-style magnetic mirror used for nuclear fusion research. Built at the Lawerence Livermore Laboratory, it was a superconducting system that generated 75,000 Gauss in the magnetic coils, and 20,000 in the center. For comparison, the Earth's field is about 0.5 Gauss. The magnet is arranged so that the field increases as one moves away from the center, thereby producing the "minimum-B" configuration that had been shown to be naturally stable. Larger versions of these same general designs would later be used on LLNL's experiments in the 1970s and 80s, culminating in the Magnetic Fusion Test Facility.