Fit acceptable

The fit of the diaphragm is acceptable. Sometimes it hooks a little and you get the feeling that something may break. So put on carefully. Also fits upside down, for example in the packaging of the camera in a bag or the lens in the lens case. (Caution - this then take prefer slightly larger).
I bought for another lens, the original Canon shutter and this can put a little easier.
The effects with and without visor I have not tested it, so can not say anything about the actual effect. Since it in size but probably no different from the original, I think it will probably work just as well.