The 2X Tele-converter for Nikon Non-AI cameras effectively increases the focal length of your lens by 2x, thus turning a 300mm lens into an equivalent 600mm lens. Your prime lens depth of field is minimized by 1/2 while maintaining the lens minimal focus distance. The teleconverter is placed between the lens and the camera. The genuine integrated circuitry maintains signal integrity between the camera and the lens. The seven element design is made of high quality multi-coated optical glass.