Celestron 71353 Cypress 10x50 Binocular (Green) BaK-4 Prisms: Increases contrast and resolution for sharper more detailed images. Fully Multi-Coated Optics: Increased light transmission through the optical path for brighter images. Waterproof and Fogproof: Nitrogen purged to prevent internal fogging of the lenses. Large 50mm objective lenses: Excellent light gathering capabilities for low light situations. Long eye relief: Extended eye relief provides a full field of view for eyeglass wearers. Twist-up Eyecups: Multiple stops for correct positioning of the eyes for comfortable viewing with or without eyeglasses. Polycarbonate frame: Strong and durable polycarbonate body. Provides structural