From David in Vermont:
I study colonial birds and have used the Duovids for 4 years. They are perfect for my needs, reading codes on banded birds. I almost always leave them set on 15 power and have no trouble holding them by hand, sometimes for several minutes in one position. They are heavy, but I often go for hours with the glasses hanging from my neck and think nothing of it. They aren't cheap, but the data I have collected because of the power and clarity are worth far more than the binoculars.