Vortex Optics Diamondback Roof Prism Binoculars 10x magnification and 42mm objective lenses, these Diamondback binoculars are the workhorse of Vortex lineup; known for impressive optical quality and durability. Dielectric, fully multi-coated lenses transmit more light and clearer, brighter images. A field of view that is one of the largest in its class helps you efficiently glass your surroundings and identify your target. A sleek, short hinge design with rubber armor and thumb indents leaves more room for your hands creating an easier, secure, non-slip grip. Multi-position eyecups twist up for adjustable eye relief. A right eye diopter accomodates for focal differences in your eyes. Argon purging and rubber armor provide enhanced waterproof and fogproof performance in extreme weather conditions.Nitrogen gas purging prevents internal fogging over a wide range of temperatures Close your right eye or cover the right objective lens with your hand. Look at the object with your left eye and adjust the center focus dial until the image is in focus. Close your left eye or cover the left objective lens with your hand and rotate the ring until the object is in focus. Blow away any dust or grit before wiping the lens. Use a can of pressurized air, soft camel hair brush, or acrylic optical brush. Gently remove smudges, fingerprints, and eyelash oil from the lens. Use a small amount of water or your breath to moisten the lens then wipe away smudges with a clean lens cloth. Isopropyl alcohol can help remove marks like fingerprints.