Always discussion about this collar and if it's worth the money. I think so. Here are some images of the stock collar, the Kirk collar, and a collage of test images. The test shots clearly show the instability of the stock collar at slow shutter speeds. The Kirk collar helps but does not totally eliminate vibration unless Mirror Lockup or good Long Lens Technique is also employed. With good technique, even the stock collar can do a good job. However, it is not always possible to use MLU. This is a very fine piece of glass and I think it deserves all the help it can get.