Review on Vivitar Series V2XMR 1 T-Mount 2X Converter for F/500mm, 420-800mm,650-1300 Lens by Kim Smith

Very easy to use, well made, the threading matches my lens perfectly and doesn't add much to the chromatic aberration or distortion despite increasing zoom capability as expected. I use it in a very basic manual telephoto lens (cheap) and it works great. Recommend for intended use. If you need higher image quality, you should look for a telephoto lens with a fixed focal length instead of using any multipliers. The seller was great too.