A many-sorted variant, called stalk format, of the single sorted tyft-format for transition system specifications, introduced by Groote and Vaandrager, is proposed. The stalk format is shown to be a convenient formalism to express continuation-style transition systems for languages incorporating concepts as, e.g., process creation or backtracking, for which the existing formats seem less adequate. It is proved, extending a similar result for the single sorted case, that for an appropriate generalization of (strong) bisimilarity for the present many-sorted setting, bisimulation with respect to a transition system specification in stalk format, is a congruence. It is argued that the several conditions, required for the type of transition system specification put forward in the paper, can not be relaxed without loosing this congruence. Finally, the present format is compared with several existing ones in the literature, viz. De Simone-, GSOS- and pure tyft-format.