HR diagram adapted from Nemec et al. (2011) showing the locations of the Kepler non-Blazhko RR Lyrae stars (squares) compared with the Blazhko stars (circles) with known luminosity and effective temperature (see Table 1). For non-Blazhko stars, the luminosity was derived from stellar pulsation models, which take into account mass loss in contrast to evolution models. The blue and red edges for the IS were computed using the Warsaw pulsation code. The fundamental mode edges (FBE, FRE) are plotted as solid lines, and first overtone mode edges (FOBE, FORE) as dashed lines. The two sets of HB models (low- and high-metallicity) are taken from Dorman (1992). The numbers on the evolutionary tracks give the masses of evolution models.