These Air Bubble Stones are made of good materials and is durable. Designed to add oxygen and circulating nutrients to your hydroponic growth system or aquarium. It is suitable for hydroponic systems, ponds, aquariums, fish tanks and other systems. Feature -Color:Grey -Material:Sandstone -Size:3.50X2.00X2.00cm/1.38X0.79X0.79in - This Air Bubble Stone has capacity for repeatedly producing of small and tiny bubbles. - You can send it as a gift for your friends who raise fish, give them a little surprise. - It has , with fine performance. Good for maintaining the health of your pet , make their daily life happier. - This bubble stone is specifically designed for large fish species such as goldfish, providing them with the necessary oxygen. - The delicate workmanship of our Air Bubble Stone will bring you a good user experience. Package list: air bubble stones