18490 and 18500 - are they the same?

[TheHashishCook]

I see some vape sites selling just one or the other, or selling "18490/18500" batteries
Is there a size difference?

 

[yzer]

An 18500 is exactly 1mm longer than an 18490. Both are 18mm in diameter. They are one or the other. I have never seen a battery marked 18490/18500.