The Swift 820ED 8.5x44 BWCF Audubon Binocular is their premium choice in a porro prism birding binocular, and is a seriously well-regarded birding unit in the ornithological community. An 8.5x power is a great compromise between the classic debate of magnification, size and exit pupil diameter. The 820ED Audubon gies an exit pupil diameter of 5.1mm, great enough for viewing in nearly all birding situations, and a very wide 8.2° angle of view that's got a great sense of three-dimensionality to it.
All of the 820ED Audubon's optics are fully multicoated, and the large porro prisms are expensive BaK-4 glass versions. This model also has an element of ED (extra-low dispersion) glass in each objective group, which helps achieve the highest-possible resolution and edge contrast, particularly in tough overcast background light.
The Audubon's robust magnesium housing has great rubber armor that's soft to the touch and silent in the field. The eyecups are the 'pop up' style, so that those with and without glasses could quickly and easily share the view.