Brian, OR means Optics Ready. When it says OR compliant, it is optics ready and is state compliant, usually meaning it comes with 10rd magazines, but could be other things depending on the state it is compliant for.
Stay safe & have a great day!

Brian, as mentioned OR is short for optics ready meaning the receiver is cut to install a optic. Compliant should have a state abbreviation before it like CA compliant meaning it's legal in California. Hope this helps.

Hi Brian and welcome. Means it is Optics Ready for the Optics of choice for the user rather than coming with a specific Optics or Sight. The user makes the decision as to the Optics they want to add. Cheers and stay safe!