Just for the record, I do not use any type of mechanical decoy. I won't go into why, and yes I realize I am in the minority here with this practice.
With that said, a guy uses these at one of my lakes and they appear to work. At least from my view about 700 yards away.
I was amazed watching him a few years ago, and to see the ducks come into his spread. It took me a while to figure out what I was seeing but when I figured it out, I realized he had himself a pretty good "magnet".
I didn't see him last year as the lake was too low and I only hunted there a minimal amount, but I am sure he still uses it. Our season in that area of the state starts next Saturday.
If I see him again and if he is still using it, I will let you know how he does.