How do I make a salad dressing bottle out of an old glass beer or soda bottle?

I was at this Greek restaurant where they had old PBR bottles with this black top that looked like a little spout. What is that spout top called? Or where can I find one?How do I make a salad dressing bottle out of an old glass beer or soda bottle?
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Restaurant supply stores also carry these, as well as kitchen stores like Williams-Sonoma or Crate %26amp; Barrel.How do I make a salad dressing bottle out of an old glass beer or soda bottle?
Pour spouts



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