Prism material, BAK4, clear image without black bars, it makes super clear and sharp images. Built in lens dust cover can prevent lens from dust and make sure you see everything in a clear detail. Waterproof, the mirror is full of the high-purity nitrogen, waterproof and antifogging. You can use it in raining day and humid environment. See things 40X closer and get clearer and brighter with 60mm objective lens and 16mm eye lens. The larger the objective lens, the more light that enters the monocular, and the brighter the image. Super Clear. The fully coated optics guarantee superior light transmission and brightness, helping you see just about any target, whether you're searching for birds or trying to get a better view of the stage.