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Hey There What Barry says is true - you can throw anything in there and it will load, as long as the category is at the end. But yes, for certain, in your case I would 301 redirect /shirts to /clothes/shirts (and all other categories). Crawl the site with Screaming Frog and keep an eye on 404 errors in Webmaster Tools for anything you might have missed. I don't think there's any issue in regards to duplicate content. -Dan