There is another Cal-Hypo 3-inch puck available under the Sustain name. I travel frequently and use this product for my daily chlorine use. I do use bleach to shock but find this puck helps me maintain my chlorine level while I'm away. The puck is not wrapped in plastic and does not erode in a day or two. Every bucket comes with a plastic dispenser and a sliding lid. It holds two pucks, which usually last approximately one week. Sustain also makes other products for shock, clarifying, etc. but I don't use any of them. I'm a BBB kind of guy who uses these pucks to maintain my chlorine without stabilizer. They have a website at www.askjoepool.com if you want to locate a dealer near you. I'm not in the pool business! I live in CT and my login name should give away what biz I am in! Cheers!