The Z-Finder Pro comes with either a 3x or 2.5x magnification and either a 3″ or 3.2″ mounting frame. There is also a Panasonic GH3 specific version. 3x and 2.5x refers to the magnification built into the lens. If you wear particularly strong reading glasses we recommend a 3x model. Otherwise a 2.5x model is usually best. The 3″ or 3.2″ refers to the size of your camera LCD screen. If you are unsure which model best fits your camera, please down load the Z-Finder compatibility chart at the top of this article. The Z-Finder Pro models offer a 40mm diameter Zacuto optical design lens, two anti-fog coating protective lens cover, a large eyecup preventing extraneous light leakage and a sturdy metal two piece mounting system.