Our toilet blue bubble cleaning block contains citric acid and sodium bicarbonate. It can effectively remove the scale, rust and other stubborn dirt on the water tank, water pipe and toilet, so that you can enjoy a spotless toilet. Its use method is very simple: 1. Take an effervescent tablet and put it in the toilet tank. 2. Let it sit for 10-30 minutes to completely dissolve. 3. Press the toilet switch to flush and clean. 4. Effervescent tablets can keep the toilet clean for 15-20 days. This product will not produce a pungent smell during use, and will emit a new smell every time you rinse and deodorize, making the toilet look new.