I have 12 - BR and 6 RIR - all 15 weeks. I kept wondering why I couldn't tell which of the RIR were roos. I mean, you'd think something would be different about them so they'd stand out right? I decided to just wait until the tail feathers came in and I'd know for sure. We tried for 4 hens and 2 roosters. Guess what? I know for a fact I have 5 roosters and possibly 6! No wonder I couldn't tell. Guess I'm not so blond after all. lol.