Consist of a flexible tubular membrane of EDI, USA make , made from EDPM, Urethane or special rubber compound fitted tightly over a PVC pipe and secured at the ends with SS clamps. The inner PVC pipe has suitable holes for admitting compressed air between the pipe and membrane which has minute holes. When compressed air is turned on, the membrane expands and air flows out through the tiny air passages in the form of enormous quantity of fine bubbles.