  This Comment addresses theoretical field limits for
superconducting-insulating (S-I) thin films multilayers discussed by S. Posen,
G. Catelani, M. Liepe, J. Sethna, and M. Transtrum [1]. It is shown that their
criticism of the SIS multilayer approach [2] to reduce vortex dissipation in
superconducting RF resonator cavities is unsubstantiated
