MARATHON BI030019 Barium Crown glass (BAK4) Porro Prism Military Grade Binocular. Compact for sports, safaris, tracking, mountaineering, bird watching and other outdoor activities PREMIUM QUALITY PRISM- Barium Crown glass (BAK4) Porro prism. SPECIFICATION- 8x magnification and 40mm objective diameter. FIELD OF VIEW- 435 ft @ 1000 yds / 145m @ 1000m. Center focus with independent right ocular adjustment. LENSES- FBMC (Fully Broadband Multi-Coating) glass coated lenses for superior image brightness. Eye Relief of 19mm. ACCESSORIES INCLUDED- Neck strap, eye-cup protectors, objective lens protectors, carrying case, lens cloth and instructions.