Sinddy 40mm Diameter Aquarium Fish Tank Ponds Ceramic Oxygen Air Stone Diffusers 1.Brand new and well packaged 2.Suitable for filteration, ponds aquarium and hydroponic nutrient tanks 3.With the sands stone construction fish tank air stone can also be chemically cleaned without the risk of damaging the stone 4.It produces fine bubbles making it efficient in the replacement of Oxygen in fish ponds, tanks or hydroponic systems.