This lens is relatively small, given its focal length - it's less than half the weight of the 300mm f/2.8 L IS. The light weight and the excellent 3-stop Image Stabilization system mean that it can easily be hand-held. One interesting feature is its ability to focus as close as 1.5m away, closer than most telephoto lenses, which allows it to be used almost as a Macro lens.

This lens can be used with a Canon Extender (teleconverter). The 1.4x Extender makes it a 420mm f/5.6 lens - an alternative to the 400mm f/5.6 prime - which will autofocus on all EOS cameras. The 2x Extender makes it a 600mm f/8 lens which will autofocus on 1D-series cameras. (On lesser cameras the 2x extender will still work, but with manual focus only.)