Medium bubbles: With numerous micro-holes that allow abundant, dense and regular microbubbles to flow from the cylinder. Air stone to aerate your water tank. Larger size: Measures 5X 20 cm (D x L). Suitable for large tanks such as ponds, gardens, some large aquariums or DWC systems. Not suitable for small aquariums. Stable in water: It is equipped with two square supports at both ends to increase its stability. It always remains stable in water and does not move easily when it bubbles. Easy to use: Soak it completely in water for more than 3 hours before using it. Clean it regularly with a brush, as it becomes clogged after weeks or months of use.