Three functions in one, Co2 bubble counter, check valve and diffuser. Acrylic material allows accurate co2 bubble reading. Easy assembling for filling up water, replacing and cleaning ceramic. Stainless steel spring check valve effectively prevents backflow. Specific material of suction pad or acid, harden resISTAnt and longer operation life. Bigger bubbles will be gathered on the surface for initial usage, the phenomenon will be vanished after 24 hours.