A method and an arrangement for determining the position of a tape-like medium are proposed. One of the filter elements has an increased effective surface area defined by, for example, a pleated surface, to provide an increased filtering surface area. The hydrogel polymer is integral to the fibers of the web. 5 mm, a portion adjacent the fillet is laser hardened to a selected depth of the wall, thus increasing resistance to stresses created in the wall when the liner is installed and operating in an engine.