Hydrofarm  AS4RD 4-Inch Active Aqua Round Air Stone
This active aqua 4-inch air stone disc is a great way to add oxygen to your hydroponic growing system. The micro-pore design energizes your growing solution as it aerates and circulates your nutrients. It will extend the life of your nutrient solutions, help keep your roots healthy and promote exceptional growth. This product weighs 0.5-pound. Measures 6-4/5-inch length by 4-4/5-inch width by 1-inch height.