Dependence of M_max on a₂ for hybrid stars involving quark matter obeying the phenomenological equation of state (3). Increasing a₂ decreases B_eff at fixed ρ_c, giving rise to larger maximum masses. We show results for two transition densities, ﹩\rho _{c}=3n_{\mathrm{sat}\,}﹩ and 2n_sat. The maximum mass is not very sensitive to the transition density.