The Current Culture H2O™ Air Flow Regulator XL is an effective tool for easily calibrating air flow into and through the aeration distribution system. This allows growers to target specific aeration rates to ensure proper aeration levels are maintained throughout the growing cycle. The Regulator is especially useful in situations where multiple Under Current® systems are supplied from one central air pump or bank of air pumps working in unison. Fits 1.5" PVC. 1-year warranty.