Simmons ProSport Porro Prism Binocular (10x 50-mm) Magnification x Objective: 10x 50mm Fully-coated, high-quality optical glass for bright, sharp, images in full-detail Bk7 prisms for brilliant light transmission Rubber armor coating for better grip and protection Porro prism system Multi-coated, high-quality optical glass for bright, sharp, images in full detail BK7 porro prisms Rubber-armored for superior grip and protection 10x magnification and 50mm objective diameter; 21-foot close focus distance; 12mm eye relief