The tuning range and functionality of superconductive insertion devices can be enhanced significantly by period length switching. Period length switching can be achieved by employing two or more individually powerable subsets of superconducting coils. In this paper the opportunities and restrictions of pe-riod length switching in superconductive undulators are discussed from a general point of view. As a particular example, the design of a hybrid supercon-ductive undulator/wiggler (SCUW) for ANKA based upon the period length switching technique is presented.