Instruct: Classify Amazon reviews into positive or negative sentiment
Query: works great!

I bought this for my dad and although I needed only 1, I bought 2 to make sure he didn't miss it. It simply works and there is no guess work so the garage door doesn't hit the back of his car. He also doesn't run the risk of crashing into anything infront of him. its great and better then a ball on a string from the celing!