These reflective clips are just good in what they should do. I'd say they're better than those traditional orange clips. I usually cycle at night and in some roads there are no illumination. With these fitted in my bike I'm sure I'm improving my visibility from both sides, which is very important when you are in a road with no illumination and come to a crossroad. But of course, don't forget the front and rear lights.
This package includes 18 clips. I put 9 evenly spaced in each wheel, which, in my opinion, is already very good. Each wheel has all clips in the same side (front wheel - left side spokes; real wheel - right side spokes -- or the other way around, it's your choice).
As already stated in other review, it is very important to clean them often (specially when raining) because they'll get dirty easily. If you let them dirty for some time, it will be difficult to clean them and that will lead you to rub them harder and scratch the reflective layer.
As a side note, there are some countries Highway Code which still don't recognize these clips as a possibility to side reflectors.