Brunton Echo 8X45 Porro Prism Water Proof Binoculars Large objective optics produces a bright, sharp image and true color. The armored aluminum frame is waterproof and fog proof-and stays that way through rugged use. BaK-4 prism glass Power: 7X, 8X, 10X; Objective diameter: 50mm, 45mm, 50mm; Eye relief: 19mm, 24mm, 20mm; Exit pupil: 7.1mm, 5.6mm, 4.6mm; Field of view: 367 ft., 435 ft., 330 ft. @ 1,000 yds.; Close focus: 13 ft., 10 ft., 16.5 ft. Waterproof