  We consider different realizations for the momentum sector of kappa-Poincare
Hopf algebra, which is associated with a curved momentum space. We show that
the notion of the particle mass as introduced recently by Amelino-Camelia et
al. in the context of relative-locality is realization independent for a wide
class of realizations, up to linear order in deformation parameter l. On the
other hand, the time delay formula clearly shows a dependence on the choice of
realization.
