Bought for filming with my camera has, what really brought the soft focusing or zooming. Unfortunately, it does not fit always perfectly on the lens because sometimes either a piece is missing, or there is just too much. Probably so no need to buy several versions, to cover all types of lenses here. I then helped me with a simple solution. With a foam rubber strips I have quasi initially formed a ring on the lens and then placed on the focus ring. This allowed me to very pleasant attach it to the lens, but also to use the same small (the diameter ago) lenses with the ring.
Then the "arm", which is purely rotated. Once purely turned, he never goes out with me sometimes. Violence I did not use, so stay the now easy in there. The pen is somewhat flexible, but the behavior and use has a positive effect. Thus, there is even less stuttering, I think.
Processing is OK, the price matches the power. It would certainly be better still, but for occasional use, the model is perfectly adequate.