Filter O-Rings for NRO-4 and NRO-5 RO Systems, package of 2, 1-Top & 1-BottomO-ring Set of Two for housings used with System NRO4-50. as EACH housing uses a DOUBLE o-ring pair. So, you'll want to order TWO or THREE SETS ( for a total of 4 or 6 o-rings ). Depending of whether you have the 2 or 3 sump housings ( NRO-4 has two, and NRO-5 has three ).
Works with -----
4 Stage TFC Reverse Osmosis Unit, 50 gallon per day production rate ( HOMERO450 is equivalent to CW5000,RO440,NRO4-50, and most other "models" of 4 stage units.)