The Canon EF 100-400mm f/4.5-5.6L IS II USM is a superb Zoom. I picked up my copy in 2017. It was the very last EF lens I purchased.  Awesome for nature and wildlife photography.  This is a big and long lens. It is a telescopic Zoom and almost doubles in length as you progress through the zoom. While  you can shot hand held, a monopod helps. I don't use this too often, but I am always pleased with the results when I do. It is really a very good lens. It focuses fast and takes beautiful images. Due to the length of the zoom and the apertures, images have a a creamy bokeh and are nicely  compressed. I've used this lens on a variety of bodies. It always delivers. This is the one EF lens I've kept after I transitioned to the mirrorless "R" cameras.  It works wonderfully with the EF/R adapter. I see no reason to sell it or trade it for the RF version.