Abstract: A filter assembly for a coolant air stream flowing through an LRU box has a base frame with a large opening superimposed on the perforated top surface of the box. A filter element is superimposed over the opening and a cover having a large opening is hinged to the base frame and latched thereto with its opening aligned with the other opening. The filter assembly is clamped by means of a harness to the LRU box with a clamping band that wraps around one end of the LRU box and one end portion of the base frame simultaneously. Spring tensioned cable sections attach to the band and extend diagonally along the sides of the LRU box and then through eyelets on the opposite end portion of the base frame so the cable develops a vertical component of force for clamping the assembly to the LRU box.