Magnetic Toilet Bowl Cleaner keeps toilet bowl water clean and clear without harsh chemicals or scrubbing. Simply place one cleaning toilet magnet in your tank. For Very Hard Water, you can use Both in the tank. The strong magnetic field prevents liming particles from forming into the crystalline material that coats and stains a porcelain bowl and tank while also working on removing all existing build up. Effective for up to 5 years, simply wipe clean to prevent buildup as needed. Set of 2 pieces plus Instructions. EVEN WORKS ON HUMIDIFIERS Feel free to message me with any questions!