Flat and round design: Maximizes the exit surface of the air stone to provide more surface area for bubbles.Made from high quality carborundum, it has strong gas permeability, uniform air bubbles and high dissolved oxygen.Benefits: Increases airflow/circulation to oxygenate the water and improve the health of aquatic life.Ornamental: Add beauty to your aquarium with this round air stone to create micro bubbles.For continued efficient use, clean the disc regularly. Features:Colour: greyMaterial: sandstoneDiameter: 13cmPackage Included:1 * Round stone disc for oxygenation diffuser Note: 1. Please allow 1-3 mm error due to manual measurement and 1-3g weight error make sure you don't mind before ordering. 2. Due to the lighting of the photos and the difference of monitors, the pictures may not reflect the actual color of the real item. Please make sure you don't mind before ordering, thank you! About Shipping: 1.please pay attention to your delivery address such as: name, street, house number, doorbell/email without name, etc. is correct, or the order will not be delivered correctly. 2.All items will be shipped within 3 business days after the payment is received. Most times you will receive them within 8-12 days then. The specific delivery time is depend on circumstances. 3.During the shopping process, if you have any questions, please feel free to consult us, we will reply you within 24 hours Hope you have a pleasant shopping experience!