1.4-stage RO water filter 2.4-stage RO system without pump 3.RO water filter RO Water Filter:Flush type:Manual FlushOutput:50GPD/75GPD/100GPDwithout pumpIt is made of the semi-permeable membrane with the the 0.0001micron filtration precision for separating and removing the bateria,heavy metal,salt,bad mineral substance and other dissolved matter and chemical drug in the runing water