Opteka High Definition 2X Telephoto Converter for Opteka 650-1300mm, 500mm and 420-800mm SLR Lenses

Doubles your zoom on the Opteka 650-1300mm, 500mm Preset, 500mm Mirror and 420-800mm T-Mount Lenses! The Opteka 2x High Definition Tele-Converter is for use with T-Mount manual focus lenses. It will multiply the focal length of your existing lens by 2x, and will cut back the amount of light by two f/stops. For example, using a 2x tele-converter with a 500mm lens will effectively increase the focal length to 1000mm. A lens set to f/2.8 will now be f/5.6. Features Focus Modes: Manual FocusBody: All MetalOptics: Multicoated HD GlassDiameter: 1.65 inches (42mm)Length: 2 inches (50mm)Weight: 2.8 oz. (80g)