Fotodiox Pro, Premium Grade Tripod Mount Lens Collar for Canon EOS EF USM Lenses, 70-200mm F4L, 300mm F4L and 400mm F5.6L Lenses as Canon A-2 Collar;

The Canon Tripod Mount Ring is the tripod collar for the Canon EF 70-200mm f/4L, Canon EF 300mm f/4L, and the Canon EF 400mm f/5.6L lens. By adding a tripod collar to your lens you can achieve better balancing on a tripod. The tripod ring also makes a big difference in minimizing vibrations. In addition, rotating the camera will now be much easier and faster. The ring is very easy to put on and take off the lens, as the lens does not need to be removed from the camera.