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
Ostrich leather applying ostrich leather as seat inserts. Many luxury car manufacturers offer ostrich leather seats from the factory. This practice is especially popular in European countries. During the 2008 - 2010 ostrich leather started to be used for sporting footwear. Well-known Mexican soccer brands such as Pirma have adopted new range of ostrich leather soccer boots launched during the 2010 FIFA World Cup in South Africa. Ostrich leather Ostrich leather is the result of tanning skins taken from African ostriches farmed for their feathers, skin and meat. The leather is distinctive for its pattern of bumps or vacant quill follicles, ranged