It amazes me how manufacturers sometimes play loose with eye relief specs on a binocular. This is an important feature for eyeglass wearers, so I can understand getting a little optimistic, but some models are not even close on the published listing for eye relief.
The published eye relief on
binoculars is eye relief measured from the surface of the lens and it does not take into account the depth of the lens inside the eyepiece tube or the thickness of the eyecup when folded down or retracted to its lowest position. As a result, the effective eye relief can be considerably less than the published eye relief on a binocular.
That's bad enough, but on some binoculars I have tested, even that is not enough to account for the discrepancy I have encountered between published
binocular eye relief and effective binocular eye relief. Since I know the exact eye relief needed with my glasses (14mm), it is pretty easy to tell when the specs miss the mark on this
binocular feature. Still, the general guideline of 15mm or more for eyeglass wearers is a good place to start.
For more on the basics of bincoular design and features, see my article at
How to Understand Binoculars