Polaris 280 & 3900 Sports Super Bag Double:

Fine Silt  Bag with double zipper. 

The double zippers are used to keep the bag closed and prevent debris from escaping the bag. The velcro is used to hold the bag upright around the feed hose

Double Zipper Bag is compatible with Polaris 3900 Pool Cleaners, also fits on the Polaris 280 cleaner