Instruct: Classify Amazon reviews into positive or negative sentiment
Query: This Stuff Works Great

I bought this product on a lark, and boy am I satisfied. I have several Thermos style hydration bottles, and coffee mugs, some of which had persistent staining from coffee consumption. These stains would not come out no matter how ardent my efforts. I used this product as directed, and those same stains came right off. I heartily endorse this product, and I will be purchasing again when I run out.