Very strong, synthetic, multi-layered bag with superior filtration. Highest quality on the market and resistant to tearing.  It is designed to maximize vacuum airflow whilst at the same time limit the amount of dust that leaks through. Fitted with a rubber membrane (gasket). It is far superior to the older-style paper bags.   For models VacuMaid P73, VacuMaid P135, plus many other brands of vacuums.