Fantechs' Rn4-4 is the most powerful model in the Radon Family The The Rn4 can create 4.3" of vacumm while moving 20 cfm of air or move 490 cfm air at 0.5" of suction. the Rn4-4 is equiped with a speed controler that can be used to dial in the fan as required. Included with every Rn4 is a pair of Fantech's 6 X 4 LDVI coupling (Low Durometer Vibration Isolator).