  For two unital Kirchberg algebras with finitely generated K-groups, we
introduce a property, called reciprocality, which is proved to be closely
related to the homotopy theory of Kirchberg algebras. We show the
Spanier--Whitehead duality for bundles of separable nuclear UCT C*-algebras
with finitely generated K-groups and conclude that two reciprocal Kirchberg
algebras share the same structure of their bundles.
