Canon Extender FD 1.4x-A Breech Lock Teleconverter for 300mm or Longer Lenses

Extender FD 1.4X Type A (for 300mm or longer lenses, except some older model FD lenses) The Canon Extender FD 1.4X Type A is a very special accessory designed to increase the focal length of long telephoto lenses with a minimum loss of light transmission. When added to Canon telephoto or super telephoto lenses, their focal length is effectively increased 1.4X, eg: 300mm becomes 420mm, 600mm becomes 840mm, etc.