The Polaris 39-310 Superbag is a large, double-chambered replacement filtration bag designed specifically for Polaris 3900 Sport or P39 pressure-side vac-sweep pool cleaners. The 39-310 Superbag is gray in color and expands to hold up to 5 liters of large and small debris within the dual-zippered chambers; giving almost twice as much debris capacity as a single chamber Polaris bag.