A functor Φp is constructed
from spaces to spectra such that, for each spectrum X, ΦpΩ∞X is the p-adic
completion of the K-theoretic localization of X. This functor is used to obtain
uniqueness results for infinite deloopings of K-theoretic spaces and maps, thereby
generalizing results of Adams-Priddy and Madsen-Snaith-Tornehave. Non-unique
deloopings of K-theoretic maps are shown to involve phantom maps of spectra, and
such maps are analyzed.