This is a set of 4 Tornado Sticks. These are replacement cartridges specifically for the Science shower heads Mirable, Mirable Plus, Mirable Zero, and ZERO. [New, Unused] The replacement目安 is approximately 1 to 3 months. (The replacement目安 varies depending on frequency of use, water quality, and usage conditions.) The chlorine removal performance varies depending on water quality, temperature, and other conditions. * The replacement frequency will be shorter if the water temperature is high (over 40 degrees Celsius) or if the chlorine concentration is high. Cannot be used with shower heads from other manufacturers. # Science Science Mirable Tornado Stick x 4 Brand: Science