1.4x (L) Teleconverter EF

"The Canon 1.4x (L) Teleconverter EF is for use on Canon EF 'L' series lenses ONLY. It will NOT work with standard Canon EF non-L lenses.Made of Canon's extra sharp Fluorite glass, the 1.4x Tele-converter will give a 40% increase in magnification to any lens attached to it, at the cost of only one f-stop of light transmission. A 200mm f/4 lens, for example, becomes a 280mm f/5.6 lens with the 1.4x Tele-converter behind it. No correction is required for either focusing or exposure operations, the camera does it all. (some focusing restrictions exist. please see specifications). As an added bonus, minimum focusing distance, for any lens, remains the same and that can really improve macro performance! Comes complete with case and strap."