And remember that the same eyepiece used differently has different eyerelief. As an example, binocular eyepieces used with long focus telescopes may have eyerelief noticeably reduced. . The instruments selected have been chosen to represent as wide a range of eyepiece performance and types as possible. The eyerelief value shown in brackets is the amount the eyelens is recessed. If the mounting was flush with the lens, eyerelief would be increased by this amount.
Some manufacturers simply throw away large amounts of precious eyerelief by poor mount design.
Many eyepieces can be transformed by simply maching away 'extraneous matter' behind the eyelens. If Machine away, then fair without glasses . When deep eyecup removed, fair without glasses. Narrow field OK with glasses but better if deep eyecup removed. Deep eyecup but satisfactory because of very small field.