the tight wedging of the valve facing strip between the valve element and the valve seat the rubber strips of the prior art were deformable so as to allow this wedging but those rubber strips were not compressible in other words the deformable rubber was moved into space available so that overall compression of the rubber could take place as opposed to that function of the rubber the present valve facing strips are compressible so that the space actually occupied by the strips under compressive forces is less than the space occupied by the strips under no compressive forces this is of course a well known function of a foamed polymeric material in a sense the foamed core acts as resilient springs which allow compression of the outer surface into the available space between the valve element and the valve seat and which function continually urges the outer surface into tight contact with the other valve member to effect excellent sealing of the closed valve as can also be appreciated the foamed polymeric core while being compressible has a high degree of resiliency in that it is not necessarily subjected to flow forces as is a solid rubber strip and the foamed core is therefore capable of continually restoring the valve facing strip to essentially the same shape of the strip prior to compression this allows the valve facing strip to be considerably larger than the space available between the valve.