Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Works Very Well

The bottoms of my toilet bowls had developed thick deposits of brown scale that I couldn't remove with a brush or a pumice stone. I poured half a bottle of this product into each bowl, let it sit overnight, and in the morning, scrubbed with a brush before flushing. Much of the scale was gone, and the rest I was able to remove easily with the end of a screwdriver. Both bowls became sparkling white with little effort.