possibility is the use of foamed polymers including open or closed cell foams the lightening element may be closed or covered with a film cap or plug in other embodiments the lightening element may not be closed in still other embodiments the lightening element may be found wholly inside the material at the ends of the roller in other words the lightening element does not extend to the ends of the roller in its use an exemplary roller 910 with lightening elements 950 as shown in fig9 of the correct size is selected for installation into an application the roller 910 has shoulders 916 and covers 952 for the internal lightening elements 950 typically a group of rollers is installed as a unit called a roller tray a roller tray consists of a multiplicity of roller assemblies 940 roller and roller rack the selected roller 910 is taken to the roller assembly for installation the existing roller is first removed by removing the retaining pin 922 and sliding the axle 920 from the roller rack 942 freeing the old roller a new roller 910 is placed between the arms 946 of the roller rack and above the base 944 of the roller rack the axle 920 is then passed through an arm 946 of the roller rack and through the central aperture 918 of the.