Frankenduals—that is, duals cobbled together from parts shared with singular and plural—have been a mainstay of linguistic theory since Jeanne's (1978) treatment of the subject in Hopi. The field has followed Jeanne in seeing Frankenduals as supporting a Hale-style (1973) decomposition of the dual into features that combine elements of singular with elements of plural. The field has been much less united in what those features are, what they mean, and how they are represented. However, a hitherto unnoticed property of Frankenduals provides answers to these lingering questions. Frankenduals display a consistent asymmetry: the morpheme shared with plural is always closer to the element interpreted as dual than the morpheme shared with singular. In Hopi, for instance, a pronominal dual results from a pronoun shared with plural and a verb form shared with singular; the reverse is ungrammatical. An explanation of this fact emerges if number features are not simply first order predicates but act on each other's outputs, and if number features are interpreted (in Frankendual languages) where they are heard. Why number features for noun would be located on verbs supports another of Hale's contentions (1986): that features are semantically abstract and category transcendent in a way that makes the featural alphabet of universal grammar highly economical.