I love these bleach pucks for the toilet tank. They really do keep the toilet much cleaner and keep rings from forming. They don't get rid of thise stubborn rings around the top edge of the bowl, that requires a lot of elbow grease to remove, but once gone, these help keep them from coming back as quickly. Also love that they don't colour the water. My only wish is that they were slightly scented. The smell of raw bleach is not the most pleasant thing to smell throughout the bathroom.