All the double couple filters are made by high uality SUS304 stainless steel,and composed by two cylinders,the inner and outer surface is polishing with 0.4μm,the top part installs the pressure meter and the drain valve,and used to clear and purify the solid foreign substance that exist in the milk,sugars,drinks,oral rehydrations and not observed by eyes.Both the filters works alternately,and the filter bag/net can be replaced without stop production.So it used for long time continous production.