Abstract: A one piece moulded blank to be folded to form a filter housing. The blank comprising a main rectangular shaped panel having a number of spaced transverse grooves forming fold lines so the main panel may be folded to form the side walls of the housing. Two end panels formed integral with the main panel and projecting from respective opposite edges of the main panel. Grooves extend along the junction of each end panel to the main panel to form fold lines so the end panels may be folded to form the end walls of the housing. Interlocking elements formed integral with the main and end panels to interlock when the panels are folded to hold the panels in the relationship to form the housing.