5 of 9 people found the following review helpful
You don't want this one!,
This review is from: Tripod Mount Ring EF for Canon EF 70-200mm F4L, F4L IS, EF 200mm F2.8L, EF 300mm F4L, EF 400mm F5.6L. (Electronics)
...you want this one instead:
The one in the link I've posted is a carbon copy of the Canon-branded design for a lot less; it has a much better spring-loaded locking mechanism than the one here, which makes the one in my link easier to swing the camera from landscape to portrait orientation. Check it out for yourself; the model you're looking at here is a completely different design to the Canon version.