Fish scale the surface, interacting only with the riblet tips, not causing any high-veloctiy flow in the valleys. Since this high velocity flow now only interacts with the riblet-tip, which is a very small surface area, the momentum transfer which causes drag is now much lower than before, thereby effectively reducing drag. Also, this reduces the cross-stream velocity fluctuations, which aids in momentum transfer too. The rough, sandpaper-like texture of shark and ray skin, coupled with its toughness, has led it to be valued as a source of rawhide leather, called shagreen. One of the many historical applications of shark shagreen was
Horween Leather Company Tack" process. Although footballs are often called "pigskins," they are made from Horween Leather Company-supplied steer hides that are embossed with a pebble pattern. The company also supplies the leather for the game balls made for the Canadian Football League, and they also supply leather to Spalding (a division of Russell Corporation) for indoor Arena Football League footballs. Horween Leather Company's leather is also used to make National Basketball Association basketballs. Horween Leather Company Horween Leather Company is an American company specializing in the manufacturing and refining of leather and related products. It is one of the oldest continuously running