The Extender EF 2x III has a protruding front element, which means it cannot be used with just any lens. It is strictly designed for: [1]
Super-Telephoto Lenses: Fixed focal length L-series lenses 135 mm and over.
Select Telephoto Zooms: Such as the EF 70-200 mm f/2.8L (and IS versions) and EF 100-400 mm f/4.5-5.6L.