Platypus Gravity Works Water Filter Cartridge works with the Gravity Works Water Filtration System to treat 4L in less than 2.5 minutes without a single pump or stroke. Unfiltered water goes into one reservoir and comes out filtered in the other reservoir. Fill the unfiltered reservoir as needed to have a constant reserve of drinking water. Quick-disconnect fitting allows for easy removal. Cartridge filters 1,500L.Manufacturer model #: 7016. Works with the Platypus Gravity Works Water Filtration System Treats 4L in less than 2.5 minutes without a single pump or stroke Unfiltered water goes into one reservoir Comes out filtered in the other reservoir Fill the unfiltered reservoir as needed Quick-disconnect fitting allows for easy removal Cartridge filters 1,500L