Product review (4 stars): Good idea, did not attach straight up for me, needs directions for me!
You have to fill this first with water before you put the ball in, or the ball will drop to the bottom, and defeat the idea of this.
Do not fill the water almost to the top as I did..(duh).
When the water freezes, put the ball on top, screw lid on.

If God forbid the ball goes to the bottom, your freezer is not working good.

That said, I found it hard to velcro this on so it would stand up  straight up!.
I tried hanging on the rack, then on the inside door.
I think if the kids are opening the door allot, that is the first place its going to start melting!
I also have a temp gauge in my freezer in the garage..

This is a good idea, but I  think its over priced.