I read that a Red sex-link was a cross between a RIR roo, and a white leghorn. Yeah, I just looked it up. Pg 111 of Storey's Guide to Raising Chickens by Gail Damerow.
I'm kinda planning my future layer flock. I figure if I get some leghorns, and barr rocks, and RIR's a RIR roo, I can get...