Leading Power Corrections in QCD: From Renormalons to Phenomenology

We consider $1/Q$ corrections to hard processes in QCD where Q is a large mass scale, concentrating on shape variables in $e^{+}e^{-}$ annihilation. While the evidence for such corrections can be and has been established by means of the renormalon technique, theory can be confronted with experiment only after clarifying the properties of the corresponding non-perturbative contribution. We list predictions based on the universality of the $1/Q$ terms, and compare them with the existing data. We also identify the scale of the non-perturbative contributions in terms of jet masses.