This paper discusses synthetic horizontal branches constructed from a grid of horizontal-branch (HB) evolutionary tracks with the alpha-elements enhanced by a factor of 5 with respect to the solar-scaled mixture and various surface helium and heavy-element abundances. The luminosity log L(3.83) and the luminosity-to-mass ratio A(3.83) of the ZAHB at the RR Lyrae gap are found to depend, for fixed helium abundance, on the total metallicity, irrespective of the adopted ratio of alpha to heavy elements. The increase over log L(3.83) and A(3.83), as the result of post-ZAHB evolution, appears rather small for the HB type in the range of -0.7 to 0.7, whereas it becomes quite significant for bluer HB morphologies.