4-Inch Round Air Stone for Aquaponics &bull; Aquaculture &bull; Hydroponics &bull; Ponds &bull; Aquariums by Cz Garden Supply (4 inch) Aquaponics  Aquaculture  Hydroponics  Ponds  Aquarium use 4" Round air stone - 6-4/5-inch long x 4-4/5-inch wide x 1-inch high Versatile Metal Air inlet uses both 3/8" ID or 1/4" ID tubing Micro-pore design aerates, circulates, and extends the life of your nutrient solution while promoting healthy roots and exceptional growth! Only available from Cz Garden Supply (TM), USPTO and Amazon Brand Registry Protected