Undersink reverse osmosis: 1.Standard 5 stage RO system 2.Food grade material Water resource:tap waterWater ... sets40'HQ:1013 sets Stage 1:(PP)5 micron sediment filter,it's effective removing dirt, rust and sand particles ... reduce of tats,odor ,and color.Stage 4:(RO)Reverse osmosis membrane ,thins film composite high quality membrand taht processes ... ,mercury, sodium.Stage 5:T-33 post carbon filter