Abstract: A fluid filter comprising a housing having first and second plastic cover members each having a peripheral flange and joined together to define a housing chamber having an inlet and an outlet. A filtration media is disposed in the housing chamber between the inlet and the outlet. The peripheral flange of the first cover member has a rib. The peripheral flange of the second cover member has a gutter opposed to the rib. The filtration media has an edge portion compressed between the rib and the gutter to form a marginal seal preventing fluid entering the inlet from reaching the outlet without passing through the filtration media. The edge portion of the filtration media is pierced and anchored by spikes which project from the rib and extend into the gutter. One of the cover members has a welding rib welded to the other cover member by a process of orbital frictional vibration welding to secure the cover members together.