Given structures $A_i$  each of cardinality $<\kappa$ where $\kappa$ is a measurable cardinal, the cardinalities of the $A_i$ are not uniformly bounded by a cardinal $\lambda <\kappa$, and $\mathcal{U}$ a $\kappa$-complete ultrafilter over $\kappa$, what is the cardinality of the ultraproduct $\prod A_i/\mathcal{U}$?