Despite differences in parsimony and philosophical orientation, physical and abstract theories of phonology often make similar empirical predictions. This study examines a case where they do not: gemination restrictions in Hungarian. While both types of theory correctly prohibit the lengthening of a consonant when flanked by another consonant, they make different predictions regarding both the relative duration changes within a target consonant and the applicability of restrictions to lengthening processes besides gemination. In two speech-production experiments, these predictions are evaluated by measuring stop and frication durations within affricates. Results show that relative duration changes occur, and that the restriction holds only for gemination, supporting an abstract theory. Yet results also indicate that gemination exhibits sensitivity to inherent durational differences between affricates, providing some support for a physical theory. Thus I argue that an adequate theory of phonology must include abstract constituents, alongside a limited, principled set of physical landmarks.