This product is a complete ripoff.
Real food grade H2o2 requires special shipping at a very high cost, but I thought I'd give this stuff a try in my hot tub.  If it was 35% food grade, I'd use 2 or 3 cups with excellent results.  I used the entire gallon of this useless product minutes after opening the package with virtually no results in my hot tub.  DO NOT WASTE YOUR TIME OR MONEY ON THIS STUFF.
Rating: 1 stars