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.