  We consider a momentum dependent relaxation time for the Boltzmann equation
in the relaxation time approximation. We employ a power law parametrization for
the momentum dependence of the relaxation time, and calculate the shear and
bulk viscosity, as well as, the charge and heat conductivity. We show, that for
the two popular parametrizations, referred to as the linear and quadratic
ansatz, one can obtain transport coefficients which corresponds to the weak and
strong coupling regimes, respectively. We also show that, for a system of
massless particles with vanishing chemical potential, the off-equilibrium
corrections to the phase-space distribution function calculated with the
quadratic ansatz are identical with those of the Grad's 14-moment method.
