FB6 Inline Filter Box The simple addition of a Fantech Inline Filter Box adds even more filtration to your home"s Indoor Air Quality system. Installs in ductwork after HRV or inline fan as an additional filter for incoming air. Includes MERV 13 filter. *10″ (250mm) depth x 8″ (200mm) height x 20-1/2″ (525mm) length *22-gauge galvanized steel with baked powder coat finish Building sciences research has shown that highly efficient filtration of the outside air before it is delivered to the home is one of the best ways to reduce the level of particles suspended in your home air.