I was attracted to these by the zoom range, the 30mm objective lens and the relatively small size of the binoculars. They do have a clear bright image at the 10x range. The focus ring on the right eyepiece is a little tight so it was difficult to know if you were changing the focus or if the rubber cover was just slipping.The major problem is when you focus at 10x and then zoom to 30x you have to refocus both sides. I tried it by focusing at 30x and then going back to 10x and now 10x was out of focus. This was unacceptable, so I returned them. The last thing I want is to have to refocus every time I zoom.