i bought a chick from tractor supply in februrary. it turned out to be a rooster and i'm not sure what kind it is. it is 7 months old and weighs about 10 pounds it is white.
https://www.backyardchickens.com/t/261208/sex-linked-information nice thread on breeding sex links. RSLs are basically a gold(red) rooster crossed with a silver(white) hen... ie Rhode Island Red X Light Sussex. The commercial birds are usually not crosses of specific breeds as such, but are mixed breed strains very specifically bred for their wonderful egg laying ability and also color so the chicks are sexable at hatch.
Red Sex Links are hybrids produced by crossing a red gene rooster (RIR, NHR, or Production Red) with a silver gene hen (WR, RIW, SLW, Delaware, or Light Sussex). The resulting offspring can be sexed from hatching by color (male chicks are whitish, female chicks are reddish) and are egg laying machines, outlaying either parent breed. It's one of the interesting quirks of hybridization.