G-LEAF 4 Inch High CFM Duct Fan & Carbon Air Filter & 25-Feet Air Ducting With 2 Clamps Combo 4 Inch 115 CFM Quiet Duct Fan (With Adjustable Two Speed Motor) 4 By 10 Inch Carbon Filter Dia 4 Inch By Length 25 Feet Air Ducting With 2 Free Durable Clamps This Combo Brings In The Fresh Air And Removes Heat From The Grow System.