"The Viper HD 15x50 Roof Prism Binocular from Vortex Optics is a high-powered binocular engineered to deliver outstanding optical performance for activities such as sports, hunting, safari, bird watching and others. The Viper series is extremely bright and steady. It performs incredibly well even in poor light conditions. Vortex's proprietary XR coatings deliver high detail rendition and rich contrast. The HD 15x50 Viper binocular is distortion free due to the HD (High-Density) extra-low dispersion glass objective lens elements which enhance image resolution and reduce chromatic aberration.The binocular focuses relatively close - 8.2 feet. It is fully multicoated on all air-to-glass lens surfaces to produce sharp edge-to-edge images. It offers a 3.3mm exit pupil and an eye relief sufficient to accommodate all viewers including eye/sunglass wearers. Waterproof, fogproof and shock resistant, it is built with a durable lightweight chassis and is rubber armored to sustain protection. As a result, the HD 15x50 Viper binocular is favored by many outdoor enthusiasts over other binoculars of its class.|HD Lens Elements: HD (High Density) extra-low dispersion glass delivers impressive resolution and color fidelity, resulting in High Definition images|XR Lens Coatings: Vortex proprietary XR anti-reflective coatings, fully multi-coated on all air-to-glass lens surfaces, increase light transmission for maximum brightness|Phase Correction: Used on roof prism models only - coating enhances resolution and contrast|Roof Prisms: Valued for greater durability and a more compact size. Ergonomic open-hinge design|Waterproof: Optics are sealed with O-rings to prevent moisture, dust and debris from getting inside the binocular|Fogproof: Argon gas purging guarantees superior fogproof and waterproof performance|Rubber Armor: Provides a secure, non-slip grip and durable external protection|ArmorTek: Ultra-hard, scratch-resistant coating protects exterior lenses from scratches, oil and dirt|Twist Eyecups: Twist up and down to precise, intermediate settings to maximize custom fit for comfortable viewing with or without eyeglasses|Center Focus Wheel: Adjusts the focus of both binocular barrels at the same time|Locking Diopter: Adjusts for differences in a user's eyes. Located on the right eyepiece|Tripod Adaptable: Compatible with a tripod adapter, allowing use on a tripod or car window mount"