Wears off after 10 days
It doesn't last a month, not even close. It vanished after 10 days. The bathroom I put it in isn't a high traffic one (may be 2-3 flashes/day). The water in the bowl gets very blue. I'm not sure if it cleans the toilet as you really cannot see very well because of the water color, but the claim that it lasts a month is a myth.
Rating: 2 stars