Canon EF 2x III Extender
Get some extra versatility from your telephoto L-Series lens with this precision-designed 2.0X extender. Your 300mm lens, for example, will double in reach, with a resulting focal length of 600mm (on full-frame cameras) or 960mm (on APS-C sensor cameras), once this extender has been placed in the light path. And it will only give up two stops 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.