Fully Multi-Coated Lenses increase light transmission with multiple anti-reflective coatings on all air-to-glass surfaces; Rubber Armor provides a secure, non-slip grip, and durable external protection; Adjustable Eyecup twists up and down for comfortable viewing with or without eyeglasses; Optics are sealed with O-rings to prevent moisture, dust, and debris from getting inside the monocular; Barrels are filled with nitrogen gas to inhibit internal fogging; Durable and compact roof prism