Yes they help a lot. Although I had them on my dually stuck on my factory "camper Mirrors" and it annoyed me. Like said above, they were always in the way no matter where I stuck them and were too small to be useful. imo.

So I took them off my dually years ago and just look over my shoulders to change lanes.

Now on a big truck they are mandatory since you can't look over your shoulder to change lanes.