This superb Denkmeier Binotron 27 binoviewer includes two matching eyepieces and a filter switch. It comes in a hard case.
Binoviewing fits the way our brains process visual information better than single-eyed (Cyclops) viewing. This is true both of binoviewers and binoculars, and is one reason that conventional binoculars are so popular in astronomy. Most users find that objects or starfields appear three dimensional. Because of the narrow spacing of the objectives, binoculars do not provide true depth perception; the brain is fooled into thinking it’s there. The same effect is observed with binoviewers for the same reason. Another effect is that bringing the same information into both eyes permits the brain to process the information differently, making subtle details more apparent. User comfort is also a very important feature of any two-eyed viewing system. It’s much more relaxing to observe with both eyes than to either ignore or close one eye.