1. They are no use.
2. They are of no use.
3. They are useless.
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<They refers to a plural form of a thing.> Which ones are correct? Are they all the same and grammatical?
2 and 3 are fine.
1 is OK, but it's lazy English!! Often I hear people say something like this, and I figure it's mostly because they've heard it incorrectly for so long, they don't know it's incorrect -- incomplete, actually!