1pcs Air Bubble Stone f74 This professional air bubble stone, made of premium material, is durable and practical with long service life. It is a great way to add oxygen to your aquarium, fish tank, hydroponic and circulation system. Great for fish tank and aquarium use. It will be the good choice for you. Features -Color: Black -Material: Sand and gravel -High temperature sintered bubble stone is made of high temperature sintering, different from the general market bubble stone -The material is strong and durable, can be repeatedly cleaned, long-term use. -Soak the product in water for 15 minutes before use. -Connect to the air pump, and put into the water to help the air pump oxygen into the water, need to connect to the air pump to have air. -The air pump you used on the surface is not enough, please replace it with a more powerful one. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.