DL 2 Pack AquaVita 4'' x 2'' Cylinder Air Stone - Aeration, Hydroponics Made from high-quality Carborundum and ceramic materials fired at 1350°C, the AquaVita Air Stones are great for aerating and circulating water in aquariums and hydroponic systems. They work especially well with our AquaVita Air Pumps! This model Air Stone is compatible with 3/16" inner diameter tubing.   Discreet Shipping and Purchase All purchases are private. All packages are shipped either USPS, UPS, or FEDEX with a discreet packaging. Most orders will be processed and shipped within 1 to 2 business days. Returns If you are not 100% satisfied with your purchase, you can return the product and get a full refund or exchange. Customer is responsible for return shipping. You can return a product 60 days from the initial purchase date. Any product you return must be in the same condition it was received and in the original packaging.