Do I need to tear off the outter protective film when I use it? No, it dissolves in the toilet tank. Brush the toilet bowl before you use it. Then take out a piece and put it directly into the toilet tank. Wait about 20 minutes, it will dissolve the blue cleaner and then you are ready to use it. How long could one tablet be used for? It depends on many factors like water temperature or room temperature or the using frequency.Theoretically,one tablet could be flushed more than 200 times at least,about last for more than 15 days. Will it hurt any parts of my toilet bowl? Definitely not. We produce our cleaning tablets from natural, gentle and safe materials. It just cleans your toilet pipes and is very safe for your septic system.