Pentax has demonstrated its mastery of optical design and user experience with the SD WP Binoculars. The binoculars have an advanced optical structure that combined with a BaK4 glass prism and fully multi-coated elements offer impressive image quality and enhanced low-light performance. Along with the optical makeup, Pentax has designed these to last and maintain performance even in adverse weather conditions. For this, there are protective lens coatings that protect your lens elements from water, oil, dust and dirt; and the binos are fully sealed and nitrogen filled which results in complete weatherproofing.