This entry-level Nikon Fieldscope model is very portable, with 50mm objective diameter. Nikon ED glass in the objective lens compensates for chromatic aberration for clear, accurate views. Multilayer-coated lenses, prisms and dustproof glass make for exceptionally bright images. The Fieldscope ED50 series model features small 50mm objective diameter to accommodate demands for more compact, light, portable and affordable models. The ED glass used for their objective lenses compensates for chromatic aberration and realizes bright, clear viewing. Waterproof construction with nitrogen gas filling makes these models fog-free when subjected to wet weather and sudden temperature changes.