: If you prefer a standalone file, select "Download offline backup game installers." Download all parts of the installer to the same folder.
: Go to the "Games" section of your account. Choose Download Method : Download S.T.A.L.K.E.R Clear Sky v1.5.10-GOG
If you are looking for this specific build (v1.5.10-GOG) on third-party "abandonware" or torrent sites, be aware that: : If you prefer a standalone file, select