Feature:1. Sturdy and durable material, can be repeatedly cleaned, long time using.2. Special stainless steel connector, more durable to use.3. High temperature firing, good air permeability, help fish to survive and breed better.4. Exquisite stone shape design, frosted surface, delicate and smooth.5. The air volume is large and the air output is even, to increase the oxygen content in the water.Specification:Condition: 100% Brand NewItem Type: Bubble StoneMaterial: Sand Stone + Stainless SteelColor: As Pictures ShownOptional Diameter: Approx. 6cm/2.36inch, 8cm/3.15inch, 10cm/3.94inch, 12cm/4.72inch, 15cm/5.91inch, 20cm/7.87inch6cm Diameter connect 4mm air tube8cm Diameter connect 4mm air tube10cm Diameter connect 4mm/8mm air tube12cm Diameter connect 4mm/8mm air tube15cm Diameter connect 4mm/8mm air tube20cm Diameter connect 8mm air tubePackage List:1 x Bubble StoneNote:NoteSoak the product in water for 15 minutes before using.Product FunctionConnect to the air pump, and put into the water to help the air pump to put oxygen into the water(need to connect the air pump to have air! Products without any accessories, need to buy).