ITEM NAME:Ball Shaped Bubble Release 5-Piece Aquarium Air Stones, 30mm Diameter, Gray L2O6 Ball Shaped Bubble Release 5-Piece Aquarium Air Stones, 30mm Diameter, Gray L2O6 Product Name : Aquarium Air Stone; Color : Gray Material : Mineral Stone Air Stone Diameter : 3cm/1.2" Weight : 106g It is for freshwater, saltwater aquarium and hydroponic use. It's used to increase the dissolved oxygen level in the aquarium. It produces fine bubbles making it efficient in the replacement of Oxygen in fish ponds, tanks or hydroponic systems. Package Contents : 5 x Aquarium Air Stone Note:Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm..It's used to increase the dissolved oxygen level in the aquarium. It is for freshwater, saltwater aquarium and hydroponic use.