I just got my Zen Ray 8X42 monocular yesterday. I agree with everything Denco said about the binocular; it's a near premium piece of equipment for a bargain basement price.
I mounted it on a tripod to compare it to my 8X42 Leica BA. Optically they were almost identical. The Leica image was slightly brighter, and maybe a little sharper. Field flatness was better in the Leica, but not by a whole lot, and was noticed more in testing than in actual use.
The depth of field appeared to be identical, and both started to soften around the edges at nearly the same point. I didn't do a star test, but CA was not apparent, although the test was done on a cloudy day. The field of view was almost identical at 390 and 393 feet at 1000 yards.
The ZR has a more comfortable view. Eye relief is 17.3 mm in the Zen Ray and 15.5 in the Leica, but that didn't seem to be the whole story. I measured the eye lens and in the ZR it is 15% wider than the Leica, a definite notch in the ZR column.
The ZR eye cup twists out, and has two click stops, although the fully extended position felt more natural to me. There is a noticeable play in the eye cup in the middle stop position, but fully extended it stays centered. However, I would have preferred a tighter click lock, although I know some people don't feel comfortable with eye cups with stiff motions and locks.
The helical focus is not as easy as some, but I actually prefer a tighter and slower focus - I find that an easy and quick focus tempts me to fidget with the focus too much. The focus ring is rubber coated and turns very smoothly - there is absolutely no play. It feels like a mini Swarovski spotting scope when focusing. Very nice.
I was worried that an 8x monocular would be hard to hold steady, but that is not an issue with a monocular of this size. With my right hand holding the base of the tube against my eyes, and my left hand turning the focus ring, I had no problem getting a steady view. Unlike smaller monoculars that you work using the tips of your fingers, this monocular can be held using the thumb and index fingers to wrap around the tube. I would have no problem ordering the 10X version, and in fact I probably will.
Another advantage of the large eye lens and bright image is that the monocular can be used "open-eyed," meaning that, for me, I did not have to close my other eye to see the image. In a small monocular, with a small eye lens and exit pupil, it's like you are staring into a small tube at a dimmer image, and consequently your view is distracted by the brighter image from the other eye. In the ZR, the situation is reversed, resulting in a much more relaxed and natural experience.
The metal alloy body looks very upscale, and the rubber coating on the focus collar is understated and nearly flush with the body. The action of the eyecup is not as rugged as on a Leica, but if I were to see a small red circle on a monocular as well made and designed as this, I would not be surprised.
I have compared this to my 5X15 Nikon monocular, my 8X20 and 8X42 Leica BAs, and my 6X30 Brunton Eterna monocular. I have also looked through monoculars from Leica, Zeiss, Vortex, and many other cheaper brands, and the ZR equals or beats them all. Part of that is a function of it's larger objective, but that would mean nothing if the coatings, prisms, eyepiece and mechanics weren't up to par. But they are. That an optical instrument like this can be had for slightly more than $100 is simply amazing