A range of optics designed specifically for marine applications. Featuring 7x Magnification Perfect For Marine Applications. Extra-Low Dispersion (ED) Glass. Phase Corrected. High Resolution Phase Corrected BAK-4 Roof Prisms. Twist-Up Eye Cups With Position Stops. Stay-On Lens Covers. Floating Neck Strap. For over a decade, Endurance ED optics have been renowned for incredible performance and reliability. Now, with the introduction of the Marine range, we have grown upon this award winning selection with optics that are specifically designed for marine and boating applications.