Review on Iron OUT Automatic Toilet Bowl Cleaner - Efficiently Repels Rust and Hard Water Stains, 6 Tablets, for Household Toilet Cleaning, Pack of 1 by Rip Twin

I've been using these for a number of years and they do a great job of keeping our toilets from red rust stains. If you have rust stains in your toilet, you must first remove the rust stains by adding some Iron Out powder by following the directions on the container. These tablets release enough Iron Out to prevent new stains, but not enough to remove existing stains. I have found that I need to put a new tablet in the reservoir about once a month, not for 45 days. Our upstairs toilets are rarely used and they still need a new tablet in 30 days.