The AD series includes roof prism binoculars with an objective lens diameter of up to 40 mm. All roof prisms in this group feature full multi-coating along with an additional light transmission coating. The A series binoculars are the compact, portable, and robust smaller siblings of the S series. Binoculars labeled WP are waterproof. With this series, users can enjoy maximum mobility without compromising on viewing comfort and optical performance. The latest binoculars from the PENTAX Sport Optics series combine over 90 years of PENTAX experience and the usual quality with advanced technologies at unbeatable prices. All PENTAX Sport Optics binoculars exclusively use prisms made from high-purity BaK4 glass with a high refractive index, and their full multi-coating is now considered the new standard coating. They feature multi-coating on all lenses, phase correction, waterproofing (JIS 6 classification), nitrogen filling, continuous rubber armoring for protection and secure grip, short minimum focusing distance, internal focusing, and Enhanced Light Transmission coating.