Abstract: Rare-Earth Barium Copper oxide (REBCO) superconductor (SC) tapes are a newly available technology that promise to revolutionize plasma and fusion research. REBCO are superconducting at liquid nitrogen temperature, providing easy access to ~1-2 tesla steady-state magnetic fields in the laboratory and, unlike standard SCs, have almost no degradation of their critical current at high magnetic fields when sub-cooled. These features allow >23 tesla magnetic coils, double the B-field of standard SC such as used in ITER, and the design of demountable SC coils. The implications of such coils have been examined in ARC, a conceptual tokamak fusion pilot plant. Exploiting the B4 dependence in fusion power density, ARC produces >500 MW in a device 1/8th the volume of ITER. Demountable coils permit modular internal components and a simple liquid immersion blanket. The compact, high-B tokamak provides for robust steady-state operational regimes with largely demonstrated physics, while high-B provides the margin to transient and disruption limits needed in burning plasmas. Critical path science and technology R&D issues are discussed that would enable this attractive path to smaller, more flexible fusion devices.