Red-dot sight measurment question.

Discussion in 'Vintage Topic Archive (Sept - 2009)' started by brjedi26, Feb 14, 2008.

  1. I decided to look into red dot sights today. And have noticed that they are measured. 40mm, 42mm, 50mm.

    So, my question is, what do these measurements mean?
     
  2. Circumference of the optical tube.
     

  3. Mike_AZ

    Mike_AZ U.S.S. Member

    2,254
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    Actually, I believe it is the diameter of the optics
     
  4. Thank you for your help.
     
  5. LOL I think I flunked that class.