Is this the most natural way to put it:

> I work in a big company. At 12 o"clock I have **an hour break**.

Or should we better say:

> I work in a big company. At 12 o"clock I have **an hour's break**.

Or even

> I work in a big company. At 12 o"clock I have **a one-hour break**.

I would go for the last version, being unsure in how widely the first two are used, under the "[leave well enough alone][1]" principle; but still I'm curious. 


  [1]: https://en.wiktionary.org/wiki/leave_well_enough_alone