Location of the four SPB-type cluster members in the Kiel diagram. Each star is given the number according to Table 12. The pre-MS contraction phase of each track is shown with solid lines, and the MS is marked by dotted lines for the range between 4 and 8 M_⊙ in steps of 0.5 M_⊙. The positions of the four SPB stars are so close to the ZAMS that even our asteroseismic modeling cannot determine whether or not they are pre-MS stars.