Position in the H-R diagram of EK Boo and other M giants, adopting T_eff from the literature, parallaxes from the New Reduction Hipparcos catalogue by van Leeuwen (2007), V magnitudes from the 1997 Hipparcos catalogue, and bolometric corrections from Buzzoni et al. (2010). EK Boo’s position (filled circles) is shown for two different effective temperatures (3420 K and 3577 K, see text). β And, another Zeeman detected M giant, is represented by a filled square. Standard evolutionary tracks for solar composition and various initial stellar masses (as indicated) are also plotted (Lagarde & Charbonnel, in prep.). Dotted lines show the evolution up to the tip of the first ascent (the RGB) for the low-mass models (1.0 to 2.2 M_⊙), while AGBs are indicated by solid lines for the intermediate-mass stars (2.2 M_⊙ and above). For clarity, only the 2.2 M_⊙ model is shown with both RGB and AGB.