These bags have ultra-micro filtration for health and cleanliness.  These bags are not the open top style but is a closed top with 3 ports that fit on a 2- inch connector tube.  One port connects to the intake valve going to the house and another port connects to the garage utility valve. These bags have a plastic cap that can be sealed when you change the bag to keep dirt from getting out.  Fits Silent Master, Modern Day, Flo Master, Air Force and Air Flo brands.  Conversion kit sold separately to upgrade open-top style bags 721-5, 721H-5, 720-5, 720H-5. Free Shipping