Increase the focal length of virtually any Nikkor SLR lens (including zoom lenses) by adding a Nikon Teleconverter. Nikon Teleconverters can be mounted in seconds between the lens and the camera, and can as much as double the effective focal lenght of the lens in use. For example a 1.4x teleconverter will increase the focal lenght of a 50mm lens to 70mm; a 2x Nikon Teleconverter will increase the focal lenght of a 50mm lens to 100mm; and so on. Please note: Nikon Teleconverters represent the same attention to detail and quality as other Nikon products. However the use of teleconverters may have some inherent limitations (for example, a decrease in f/stop). Also, Nikon AF/AIS lenses must be manually focused when used with teleconverters. TC-300 2X Teleconverter for most Nikor AI lenses 200mm or more.