The Fluidmaster 8302P8 Flush n Sparkle Automatic Toilet Bowl Cleaning System Bleach Refill Cartridges are designed for simple and effective hands-free cleaning for most toilets with every flush. Flush n Sparkle Bleach Refill Cartridges are made to quickly replace old cartridges and fit both the Bleach or Blue Systems. Installation is easy and takes only a minute for continued hassle-free cleaning. The Flush n Sparkle Bleach Cleaning System puts a powerful bleach cleaning solution directly into the overflow tube of the flush valve so no chemicals ever touch the flapper fill valve or other tank parts. Preventing the damage drop-in tablets normally inflict leading to deterioration and part malfunction. The Flush n Sparkle Cleaning System Refills offer a powerful toilet cleaning solution in a 2-Pack for up to 6 months of cleaning.