Please note that I am an optics amateur at best and cannot provide detailed technical information regarding this product. I also cannot compare how this monocular stands up to its competitors, as it is --as far as I can recall-- the only monocular I have ever tested. My only point of comparison are my trusty old Nikon Monarch 8x42's.
I bought the Vixen 6x16 in February 2021 after a long search for a monocular I could put in my pocket or in my purse for emergency birding. I was looking for something extremely compact and lightweight, not too expensive (my budget was more or less USD$100), but good enough to be of use in the field and anywhere else. Other monocular choices were discarded because they were too large, too heavy, had poor close focus, or exceeded my budget. Vixen's 6x16 stood out because of its compact size (7.1 x 3 cm) and low weight, and because most reviews highlighted the surprisingly good quality of its optics in spite of its size and price. I was also attracted by the fact that Vixen's multi monoculars were designed with art enthusiasts in mind, as the sharp optics and extremely close focusing distance (25 cm on the 6x16) mean they are ideal for taking to exhibitions where visitors can't put their nose up to the artwork.
1. CASE AND ACCESORIES - Nothing special here. The monocular came with an impractical faux-leather pouch that didn't fit well enough for my taste. I ended up replacing it with another pouch. The neck strap is simple, too, but I haven't had any issues with it after one year of use. I tied the case and lens covers to the neck strap hook to avoid losing them.
2. BUILD - Lovely, but not waterproof (although I haven't tested this), so keep that in mind before submitting them to abuse. The Vixens are made in Japan and they're built like a quality photographic lens. No plastic in them as far as I can tell. No rubber coatings or additional impact protection except for a rubber grip, but I've dropped them several times while they were inside the case and they seem to have held up fine. I love holding them but I imagine they might be a bit difficult to use in larger hands (I'm female and fully extended my hands measure about 20 cm from the tip of my pinky to the tip of my thumb).
3. OPTIC - Obviously dimmer than a pair of 8x42's, but the image has the sharpness you would expect to find in a decent low-to-mid range binocular. I was quite impressed with it. Distortion around the edges isn't too bad. Good contrast. Bright, but my impression is that it gathers as much light as a naked eye does so don't expect it to perform well in low-light conditions. Here's my attempt at digiscoping with it:
4. EYE RELIEF - Almost none. You can manage to use it with glasses but of course field of view suffers.
5. USE - It takes a while to get used to them, but with practice I've become adept at locking them on to target very quickly.
Overall I'm very happy with this little beast --I take it with me absolutely everywhere.