Features: brand new and high quality The air stone disc with shell will create abundant small to tiny bubbles quietly, rather than a limited number of larger bubbles. Can be easily driven by even nano air pumps, suitable for aquarium, fish tank and circulation system. Increases oxygen and lowers CO2 levels. Made of high-quality high temperature fired sand stone, sturdy, durable & washable, safe to your fish. The air stone disc can be easily disassembled by twisting, to replace new air discs. Size: Three sizes, suitable for most small, medium, and large fish tanks. Specifications: Material: High Temperature Fired Sand Stone Color: White Size (Approx.): 1-Diameter 35mm/1.38in 2-Diameter 50mm/1.97in 3-Diameter 100mm/3.94in Weight (Approx.): 300g Package Includes: 1 Piece Air Stone Disc (3 Sizes) note: 1.Please allow 0-1cm error due to manual measurement. pls make sure you do not mind before you bid. 2.Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you!