How do I know it's great you ask? Good thing I had ACETONE on hand because whoever packaged this product must have known it was leaking due to a loose lid because they put it in a second bag that contained the product. Needless to say, it was a very sticky mess. That being said, having cleaned the bottle, stopper, and cap as best I could I feel like it did its job really well. It took me a while to get the stickiness off my hands, but let it be known a can of ACETONE will do the job too!