Plants grown in rdwc setups have easier access to oxygen and nutrients, which means they spend less energy searching for nutrients and developing roots. As a result, plants will reward you with fast vegetative growth and excellent yield. The water pump sends the nutrients in the lower 1" tubing up through the 1/2" tubing and into the controller unit recirculating the nutrients. Root box hydroponics grow 2 lower feed rdwc system includes- (2) 12 gallon grow modules with bulkhead screen fittings to prevent water pump clogging, (1) 5 gallon controller unit, float valve w/ green inlet fitting (2) 10" net pot lid baskets (1) 635gph commercial air pump & 6 outlet air divider (1) 400gph water pump & inlet outlet fittings (6) 2" round blue air stones (6) airlines (12) steel bulkhead hose clamps, all pump tubing/fittings, bulkheads, module fittings & instructions included for a quick easy install. System fits inside a 3'x3' grow tent.