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Message: <blockquote data-quote="Steve C" data-source="post: 3662038" data-attributes="member: 56622">Dennis,Personally I think you have this backwards.  <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite2" alt=";)" title="Wink    ;)" loading="lazy" data-shortname=";)" />  The eye relief is set by design.  What has to be done is to match the eye cup extension to the eye relief, the opposite of your quoted line above.  Maybe that is what you meant and I don't want to seem to be nit picking here.Many binocular eye relief specifications are pretty close to the same.  This means many binoculars can be used with the same or similar eye cups.  There are a lot of people, those clustered close to the mean in the eye relief bell curve who can use most any eye cup assembly.  There is a lot of variation in users, so there is no one size fits all.  I know Maven tries to adhere to the extension vs eye relief and GPO has done an exemplary job with the eye cup assemblies on their new binoculars.  It seems to me the greater the actual eye relief, the greater the need for extra extension.  However, I can't speak for manufacture of binoculars in general as regards your question.  In general I would venture to comment that most of the binoculars in my experience have less eye cup extension than specified eye relief.</blockquote>