AC Infinity Inline Filter Box 6" with High Efficacy Filter, Whole House HVAC Filtration Kit, Fits 6-Inch Inline Duct Fans for Fresh Air Intake and Ventilation
HVACQuick - HVACQuick CFB-HP Series HEPA Inline Filter Box
Air Filter Box with High Efficacy Filter, 8-Inch - AC Infinity
In-Line filter Box - Greentek
Inline Filter Box - All Round HVAC
Fantech FGR12 Filter Cassette With Panel MERV5 Filter
Filter Box For 4'', 5'' or 6'' Diameter Duct Connector with MERV8 Filter by S&P| KitchenSource.com
Air Filter Box with High Efficacy Filter, 4-Inch - AC Infinity
Fantech FB 6 6 inch Duct Inline Filter Box
Spectre Inline Air Box 6in. w/Filter - Fuel Injector Connection