Matala Air Discs are available in a 9 inch diameter and are designed for the wastewater treatment industry to very high standards. The air pore size in the rubber membrane is designed to give a medium size bubble which will not put any significant back pressure on the system. In fact this special air disc only adds less than 6 inches of water depth back pressure. The 3/4" male thread makes it easy to attach to your feed line. The 9 inch disc is capable of safely handling air flows of 25 lpm to 80 lpm.