Fantech PB110 Inline Exhaust Bath Fan Kit, 110 CFM, Remote mount fan, for 4" duct: Industrial Hvac Fans And Circulators: Amazon.com: Tools & Home Improvement
Fantech FG4 139 CFM Centrifugal Inline Fan with 4 inch Duct Opening
375 cfm Max., 6 in Duct, In-Line Duct Fan - 15W763|RN3 - Grainger