Designed to attach between a Canon DSLR and Canon Lenses w/ Focal Lengths above 300mm. (Eg. Canon EF 300mm f/2.8L IS USM II, Canon EF 400mm f/2.8L is III USM) Will not work on lenses such as 75-300mm, 100-400mm, etc. This 2x Teleconverter doubles the magnification of the connected lens, dramatically boosting its apparent focal length with a minimal increase to the size or weight of the camera and lens combination. Help to ensure clarity while reducing ghosting and flare. Front and rear lens caps as well as a pouch are included for storage and transport.