Rawhides consist of a network of three-dimensional connected, finest skin fibers. These fibers are not equally entangled at all parts of the body. In the back section the structure is tight and closely meshed, in the abdomen section more loose and with bigger gaps. Also in the neck the skin structure is loose, in addition skin folders make a maximum of freedom of movement for the head possible.
All of these physically caused differences have an effect in the process of the manufacturing of leather. Because of varying density of fiber the skin absorbs different amounts of dye into the tissue. Like this differences in color occur between leather pieces of parts of the body with tight and loose tissue structure.