Vortex Optics Viper HD Binocular Cases The Vortex Optics Viper 42mm Roof Prism Binocular Case is a replacement for the case supplied with most Vortex Optics 42mm roof prism binoculars. There is an interior pocket which is a convenient place to store a license or keys. It has a quick-release buckle system and a multi-function belt loop attachment that slips over backpack straps as well as belts. The case is made from Cordura nylon with a soft padded interior.