The Grundfos Inlet filter is a recommended accessory to protect the pump from sand, gravel or other debris, when pumping rainwater or well water. The square mesh allows a uniform flow along the entire surface of the cartridge itself, which minimizes the possibility of clogging. The smooth surface of the filter ensures easy washing and cleaning. The filter cartridges provide a nominal filtration with an efficiency of 80%. If properly used, they can be used repeatedly maintaining constant efficiency. The inside core is manufactured from talc filled polypropylene and a welded nylon net.