The AP series includes Porro prism binoculars with objective lens diameters of up to 40 mm. In addition to full multi-coating, they feature an additional light transmission coating. The binoculars in the A series 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 consistently high quality with advanced technologies at unbeatable prices. For all PENTAX Sport Optics binoculars, only prisms made of high-purity BaK4 glass with a high refractive index are used, and their full multi-coating is now considered the new standard coating. They feature multi-coating on all lenses; are waterproof; nitrogen-filled; have a continuous rubber armor for protection and secure grip; a short minimum focus distance; internal focusing; Enhanced Light Transmission coating; and long eye relief.