The teleconverter doubles focal length of a lens or a telescope, so if you have a lens or telescope with focal length of 500mm, the converter will increase it to 1000mm.
The converter has been constructed upon lens made of the highest-quality optic glass and features anti-reflective coatings. It also comes with a T2 mount, so you can use it for all lenses or telescopes fitted with this thread. The converter also causes double loss of light in the lens. For instance, when attached to a lens or telescope with f/5,6 light factor, the converter will reduce this value to f/11.