The two models share most of the same features, the chief differences being magnification (10.5x as opposed to 8.5x), relative brightness (28.1 as opposed to 18.5) and apparent angular field of view (50.1 degrees as opposed to 60 degrees). Shared features include outdoor-oriented features like waterproofing (for up to 10 minutes), O-ring seals and nitrogen gas protection, all of which protect against the elements. The carbon fiber/glass-reinforced polycarbonate resin, which Nikon promotes as being especially durable, is also a shared feature. The phase-correction coated roof prisms (for high resolution images) and multi-layered coated lenses and prisms of the two models (for bright images) make for high-quality watching. Like many of Nikon's binoculars, the Monarch X 8.5x45s are made with Eco-Glass, which means that they contain no lead or arsenic.