Clorox chlorine for pools. This seller needs to be taken off of Amazon. I did not read the reviews, therefore I did not realize that this was not the 25 lb tub with 300 3" discs like is advertised from other vendors. Seems like this is a purposeful scam by the overseas crooks. I ordered this because it looked like the tubs of regular 3" discs. It advrtises 300 discs just like in the big tubs. This seller needs to be taken off.