Built to withstand extreme nautical environments, the Bushnell Marine 7 x 50 Roof Prism binocular w/compass are buoyant, waterproof and corrosion resistant. Multi-coated optics and premium BaK-4 prism glass offer bright, clear, crisp viewing and superior light transmission and brightness. A rugged rubber armoring provides a sure grip, absorbs shock and keeps them from sliding in rough conditions. O-ring and hermetically sealed, and nitrogen-purged to keep out moisture, all Bushnell Marine binoculars are 100 percent water- and fog- proof and highly resistant to saltwater corrosion. In other words, they're essential equipment if you spend a lot of time on -- or occasionally in -- the high seas. And did we mention the built-in compass?