  For scalar perturbations of an extreme Reissner-Nordstr{\" o}m black hole we
show numerically that the Ori pre-factor equals the Aretakis conserved charge.
We demonstrate a linear relation of a generalized Ori pre-factor -- a certain
expression obtained from the late-time expansion or the perturbation field at
finite distances -- and the Aretakis conserved charge for a family of scalar or
gravitational perturbations of an extreme Kerr black hole, whose members vary
only in the radial location of the center of the initial packet. We infer that
it can be established that there is an Aretakis conserved charge for scalar or
gravitational perturbations of extreme Kerr black holes. This conclusion, in
addition to the calculation of the Aretakis charge, can be made from
measurements at a finite distance: Extreme Kerr black holes have gravitational
hair that can be measured at finite distances. This gravitational hair can in
principle be detected by gravitational-wave detectors.
