Quad 440 & 420 extended surface air filters shall be manufactured of 100% non-woven polyester. The air entering side shall be a highly lofted, coarse fiber, designed to facilitate the depth loading of dirt particles, thus acting as an integral prefilter for the more dense second stage. The air leaving side shall incorporate a skin backing. The filter shall be manufactured to fit existing hardware and shall retain rigidity under varying air volumes. The outer and center edges of the individual pockets shall be thermally sealed. The pockets are sewn together and supported by a heavy-duty cross wire, which insures maximum rigidity and eliminates the possibility of element detachment. There shall be sufficient media overlap to ensure a positive seal between the filter and holding frame, eliminating the possibility of air bypass and the need for supplemental gasketing. All filters shall incorporate media that is Class 2 under U.L. std. 900. The Quad 440 shall achieve a MERV 7 rating when tested in accordance with the ANSI/ASHRAE 52.2 Test Standard.