Pentax SP 16 x 50 Porro Prism BinocularsDesigned for both astronomical and terrestrial use, Pentax's 16x50 S Series SP Binoculars feature large oversized fully multicoated 50mm objectives to reduce reflection and maximize light transmission through the entire optical path. Utilizing the traditional porro prism configuration gives scenes a rich depth of view for an immersive observation experience and provides a comfortable feel in the hand with a lot of surface area to maintain a sure grip.