 The typical age of these systems is about 150 Myr with a range of 50-200 Myr.They show a significant density of binaries and a large number of optical binaries.The stars of these OCRs have a trend to be massive and hence early-type (A-F) stars although this observational method includes a noticeable selection effect because bright early-type spectra are easier to detect than fainter and later ones.