100% brand new and high quality,Increase oxygen levels, lower CO2 and raise PH.It is an important instrument to successfully keep aquatic fish for respiration process.Durable, washable and sintered by high temperature.Creates bubbles in fish tank while attached to an air pump(air pump is not included).Creates water currents and dazzling underwater scenes.Color: GrayMaterial: Mineral Stone + PlasticItem Size: Approx. 40mm * 15mm (D * H)Item Weight: Approx. 30g / 1oz/ pcsThis air stone is suitable for using in 30-60cm fish tanks.Suitable for inner diameter 4mm soft tube.Before use, please immerse it in the water for 15 minutes.It it doesn't have bubbles in one part, please change the pump of higher power.It will not work as normal if you attach to the submersible pump.Package List:10 * Air Bubble StoneOnly the above package content, other products are not included.Note: Light 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.