I purchased this eyepiece to accompany my Kowa TSN-883 spotting scope body that I used on an 11 day sheep hunt this fall. I used this eyepiece extensively and found it to perform flawlessly through all conditions of light and weather. I was pleasantly surprised to see that at full magnification of 60x power that the edge to edge clarity, clear picture, and light transmission was amazing. The old spotting scopes I'm used to would be almost useless at full magnification, this eyepiece changes that!
Pros: 4 position eye relief, I found the 3rd position worked perfect for my Phone Skope adapter, while the 4th position was best for my eye. Lightweight compared to top competitors. No loss in clarity, light transmission, or clear picture at all spectrums of magnification. Clear image of animals from 150 yards up to miles away, I ultimately decided on a legal ram from over a mile away.
Cons: I was hunting near a glacier, and some silt did make its way into the eye relief grooves making it not as smooth to change the position of the eye relief, although I don't know if that could have been engineered differently really. This is the only con I can reasonably think of.
If you are wanting top of the line performance without the name brand price that Swarovski carries, absolutely purchase the Kowa, you will not be disappointed.