This tripod mount ring is compatible with selected Canon telephoto lenses, giving photographers an alternative point at which to attach a tripod. When shooting with long lenses, excessive strain can be put on a camera’s lens mount by long or heavy lenses, however this tripod mount ring provides a more balanced set up. Compatible with EF 400mm f/5.6L USM, EF 70-200mm f/4L USM, EF 70-200mm f/4L IS USM and EF 70-200mm F/4L IS II USM lenses.