In-Tank Drop-In Blocks are an automatic in-tank toilet bowl cleaner. Each block is wrapped in a water-soluble wrapper so there is no plastic or glass packaging to throw away. They clean and deodorize the toilet bowl with every flush for up to 1,200 flushes. Just drop the 2.5-ounce block into the toilet tank and you're done. You get a clean fresh toilet bowl with every flush.