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Glossary of Terms

Uni-Fly™
Found in Merrell’s range of trail runners and walking boots, Uni-Fly™ is the name of their shock absorption system found in the midsole and outsole of their footwear, helping to promote comfort and greater stability.
Unit Bottom
A single shoe bottom made from a mold of rubber or plastic.  It includes the sole, platform heel or wedge.
Upper
The upper part of the shoe, not including the sole.  May be made from leather, fabric or synthetics.
Upper Leather
Any leather used for making shoe uppers.  The principal leathers used for shoe uppers are calf, kid, horsehide, goat, sheep and leathers made from the skin of reptiles.  All of these may be made in a wide variety of finishes, such as smooth, suede, patent, embossed and glossy.