Features: OOTDTY Practical and durable home using product. The bio-sponge inside provide more surface area for growth of beneficial Bio-Spira BIO-Balls do not require replacement unless damaged or destroyed. The bio balls provide biological filtration, removing toxic ammonia and nitrite. Each filter media is pre-packed in its own mesh media bag. Can be reused over and over again until it breaks. In the event of excessive buildup, you may gently rinse with water from an established aquarium, if desired. Great for fresh or saltwater aquarium filtration systems. Specifications: Material: Plastic Aquarium Pond Balls Dimension:Diameter of bio ball: 16mm/0.63(included biological cotton) Color: Black Quantity: 100 PCS Package Includes: 100x Bio Balls(No retail package) Note: 1.Please allow 1-3cm error due to manual measurement. pls make sure you do not mind before you bid. 2.Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you! _x000D_