A search through literature reveals four methods in order to derive the mass of WR progenitors, i.e.

a. WR stars must be descendant from the most massive stars which share their galactic distribution,

b. the computation of detailed evolutionary models of massive close binaries up to the WR phase, able to explain the observational constraints of these WR binaries,

c. comparing the very narrow mass-luminosity relation of massive core helium burning stars predicted by evolution and estimated bolometric luminosities of WR members of stellar aggregates,

d. the minimum mass of the progenitor of a WR member of a cluster equals the mass of the most luminous star (or the star with the earliest spectral type) in the cluster.