Swift Sport Optics has added a roof prism version of the world famous Audubon binocular. Using the same renowned 8.5x, 44 optical formula, BaK4 prisms, twist-up eyecups, and lightweight rubber armoured body as the porro prism Audubons. The Swift 828 offers fully multi-coated optics for high resolution viewing, close focus to under 9 feet and a comfortable 19mm eye relief. The latest models incorporate a left diopter adjustment operated from the center focus knob for a more convenient quick focus. Equipped with a neoprene neck strap, rainguard and objective lens covers, microfiber lens cloth and padded field case. Features: 5-Lens Ocular System • BaK4 Prisms • Fully Multi-coated Optics • Center Focus Diopter Adjustment • Waterproof, Fogproof and Shock Proof • SwiftPremier Twenty Five Year Warranty Specifications: Prism Type Roof, 8.5x44 • Objective Diameter 44mm • Field of View @ 1000 yds/m 336ft/112m • Weight 23.4oz/664g • Close Focus under 9ft/2.7m • Eye Relief 19mm • Prisms BaK4, Phase Coated • Lens Coating Fully Multi-coated • Interpupillary 57-73mm • Armoured Rubber Armour • Eyecups Twist-up • Waterproof Yes