Fully Multi-Coated Optics increase light transmission with multiple anti-reflective coatings on all air-to-glass surfaces; Nitrogen gas-purged and o-ring sealed for fogproof and waterproof performance; Rubber Armor provides a secure, non-slip grip, and durable external protection; Adjustable Eyecups twist up and down for comfortable viewing with or without eyeglasses; Center Focus Wheel adjusts the focus of both binocular barrels at the same time; Right Eye Diopter adjusts for differences in a user's eyes.