Aqua-Pure(TM) Parts, Cartridge Adapter, 1 per case, 6899831 Allows you to stack and create a 20 inch filter For use with3 maqua-pure Ap111, Ap117, Ap124 and Ap420 water filters Genuine OEM product For Models: AP801, AP801-1.5, AP802, AP802-1.5 Fits all new Models Genuine Factory Part