Abstract: A filter media is formed into a filter bag for fluid filter elements. A long tube of filter media is formed into a helix or a pleated structure with a corrugated cross-section to increase the surface area of filter media area that can fit into a given volume. A retaining structure can be used to maintain the shape of the filter media.

Abstract: Some embodiments of the disclosure are directed to a fluid filter assembly including an outer filter element having a hollow core and an inner filter element having a hollow core. The inner filter element can be positioned within the hollow core of the outer filter element, thereby defining an internal fluid passage. In some embodiments, the first end of the outer filter element and the first end of the inner filter element can be supported by an open endcap assembly, which can also include a fluid inlet in fluid communication with the internal fluid passage. In some embodiments, at least one of the filter elements can include a pleated filter media.