Check the listing for details. Active Aqua Air Stone, Cylinder, Large, 2" x 4" x 1/4" - oxygen diffuser. Condition: New. Listed at 8.79 USD. Active Aqua air stones are an ideal way to add oxygen to your hydroponic growing system. The micropore design energizes the growing solution as it aerates and circulates nutrients. Air stones will extend the life of your nutrient solution, help keep roots healthy, and promote exceptional growth.Choose from three versatile cylinder sizes. This one is 4" long by 2" in diameter, our largest cylindrical air stone available. Fitting accepts 1/4" air tubing.An ideal way to add oxygen to your hydroponic growing systemMicropore design energizes the growing solution as it aerates and circulates nutrientsAir stones extend the life of your nutrient solution, help keep roots healthy, and promote exceptional growthPump and aquarium not included.