DBF1 Dryer Duct Booster Fan 4 Inch Duct No Clog Motor located outside the air stream and features a material handling wheel. IT WILL NOT CLOG WITH LINT (other brands require cleaning every 6 months). Backed by a 5 Year No Clog, No Maintenance Guarantee! Includes instructions, hardware packet and mounting bracket. ACTIVATION MEANS NOT INCLUDED. PRESSURE SENSOR, CURRENT SENSOR AND TIMERS SOLD SEPARATELY.