Canon EF 1.4x III Extender
Get some extra versatility from your telephoto L-Series lens with this precision-designed 1.4X extender. Your 300mm lens, for example, will gain 40% more reach, with a resulting focal length of 420mm (on full-frame cameras) or 672mm (on APS-C sensor cameras) once this extender has been placed in the light path. And it will only give up one stop of light sensitivity in the process. It's like getting two lenses out of your kit bag when this extender is standing at the ready.