Swift Audubon 828 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 armored body as the porro prism Audubons. The 828’s offer fully multi-coated optics for high resolution viewing, close focus to under 9 ft., and a comfortable 19mm eye relief. The latest model incorporates a right diopter adjustment operated from the center focus knob that makes focusing easier and faster.