Floating Prism System uses flexible silicone lens mount to absorb severe shock, impact and abuse without damage; Compact Design is comfortable to carry; Sports-Auto Focus System for less constant adjustment; Makrolon housing is durable polycarbonate with NBR Long Life rubber armoring; Fully multicoated optics for the ultimate in brightness and resolution; Individual adjustment allows for ocular differences; Waterproof for use on boats and in inclement weather