while the airflow and direction of compression are the same as shown in fig6 it is also obvious from the photograph that besides the density being less than is shown in fig6 the fibers are more in a random array than the more horizontally oriented fibers in fig6 the combination of a fiber charged fixture with a compressing load such as is shown in fig3 can be introduced into a heat treatment unit e g a sintering furnace the load on the fiber mass restricts expansion during heating assuring that the resultant structure will have the desired dimensions and eliminating the need for time consuming sizing and trimming this method also obviates the need for multiple heat treatment steps because the fibers are joined together by sintering in a mass of the size and shape of the final product and the mass is joined to its backing ring by brazing simultaneously or in the same operation thus requiring only one heat treat operation also the hot deformation step required to permit work with low ductility materials such as materials containing nickel aluminides is no longer necessary with the present invention furthermore intimate contact in the fiber mass in the fixture cavity is achieved before sintering making it possible to more closely meet prescribed size tolerances finally products made according to the present invention have no seam prior art products with seams are undesirable because such seams present a path for low gas flow resistance reduced gas flow i e reduced permeability is a result of the density gradient and fiber orientation of products made according to the present invention for a given gas and a given porous material under steady state flow conditions the permeability coefficient is inversely related to the pressure drop of the material at constant air flow.