  Shear and bulk viscosity-to-entropy density ratios are calculated for the
pure gluon matter in a non-equilibrium mean-field quasiparticle approach within
the relaxation time approximation. We study how different approximations used
in the literature affect the results for the shear and bulk viscosities. Though
the results for the shear viscosity turned out to be quite robust, all
evaluations of the shear and bulk viscosities obtained in the framework of the
relaxation time approximation can be considered only as rough estimations.
