Bolt of Silk Cloth is one of several types of cloth that a tailor can use to make different types of armor. It is crafted, looted and sold by NPCs.
Silk Cloth - Item - World of Warcraft
Category:World of Warcraft tailoring crafted items, WoWWiki
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Silk Cloth - Wowpedia - Your wiki guide to the World of Warcraft
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Pattern: Crimson Silk Shoulders - Item - World of Warcraft