White factoring affects the amount of white on the dog. It is hard to tell, without actually breeding, whether a dog is white-factored or not, though dogs with white going up the stifle (the front of the hind leg) are usually assumed to be white-factored. Breeding two white-factored dogs can result in color-headed whites — Shelties with colored heads (sable, tricolor, bi-black, or blue or sable merle) and white bodies. For show dogs, dogs more than 50 percent white are heavily penalized and thus are not shown in the breed ring; they are normal in every other way.