The fibers are woven in a three dimensional pattern. The chemical properties of collagen, the predominant component of skin, give it a distinctive porosity or breathability. Leather can absorb up to thirty percent of its weight in water vapor without loss of dryness. It is also noted to have a stress-strain performance which consists of an optimal combination of firmness, softness, and elasticity. Leather also retains its shape well.
Tanning gives leather the ability to resist the aging process well.
The refinement of high performance leather has resulted in features that include improved water repellency, low water absorption, fast and soft drying, and durability. At the beginning of this century, steel was the only material noted to be useful for foot orthoses. In the 40 s and 50 s some leather combination devices were used to supplement the steel ones in common use. Later, a full length leather device, the Levi mold became popular. Today acrylic devices dominate the marketplace, but there is still much life in the old fashioned leather material.