[en] For the 0.8-GeV storage ring BESSY in Berlin an insertion device to be used as undulator and wiggler (k = 0-6) is currently under construction. The pure permanent-magnet structure consists of 35 periods with 7-cm period length. The influence of operating this structure with the small emittance optic METRO was studied quantitatively in linear-synchrotron theory by modeling the multipole structure by hard-edge dipole magnets. Working point, betatron functions, etc. were studied as function of the K parameter. It turns out that vertical focusing can be compensated sufficiently well for fields 12 kG or less by detuning the two adjacent quadrupoles. The model calculations were checked by calculating trajectories through the full three-dimensional magnetic field by solving the equations of motion. As expected, vertical focusing is overestimated in the hard-edge model by about 20 percent. 12 references