Air Discs are great for aerating or circulating nutrients in your tanks or reservoirs. These air discs incorporate suction cup feet to keep your air disc secured without fear of it moving around or flipping. The air disc has a built-in 3/8 inch 90 degree elbow fitting that insures the airline connects freely to your fitting and prevents the air line from kinking at the base of the fitting. Comes in three different sizes 4 in, 6 in and 8 in.