These replacement bags offer the greatest airflow least differential pressure and best overall efficiency available. micro-porous to shed dust and dirt so bags empty quickly and completely. envelope style. • 2.5 microns. captures the finest most hazardous dust • bag material: felt • upper replacement bag for the g1028 g1029 and g1030 series dust collectors as well as the w1666 dust collector • recommended by fine woodworking issue #133.