Check the listing for details. Crazy 2"Air Stone Ball Plus Bubble Aerator Diffuser for Aquarium Hydroponic. Color: Gray, Condition: New. Listed at 8.99 USD. Makes Lots of BubblesAquarium air stones moderate in size and outputs a large steady stream of tiny bubbles, no leaks, add enough oxygen to your fish, and also make your fish tank more beautiful.Air stones extend the life of your nutrient solution, help keep roots healthy, and promote exceptional growth. This stone is a must have for your aquariums. FEATURE·Widely applicable: Suitable for hydroponic systems, circulation systems, aquarium fish tanks, helping extend the life of your nutrient solution, keep fish/ roots healthy and promote plant growth·Unique feature: Abundant Tiny Bubble, this 2" crazy air stone will create much more abundant cascade of tiny bubbles than you can ever imagine·Air Stone Dimension: 2 "D; Connector Diameter: 3/16"/4 mm or 3/8"/9mm Specifications1. Color: Gray2. Material: Silicon carbide, plastic3. Suitable occasion: fish tank, aquarium, hydroponics and so on4. Size: 2" D (5mm)5. Each Weight: 117g/4.1oz Notes·Please soak the air stone in water for about 30 minutes before first use.·If the air stone doesn't have bubbles in one part, please change the pump of higher power.·After a long-term usage, please clean it if bubbles lessen.