Ultima V, VI, 4 Stage Filter Pack Includes all the filters and O-rings for your Ultima V, VI, and&nbsp;4 stage RO systems Keep your RO system at peak performance with quality OEM filters Works with GE GXR10, International Filter RO4, Watts 4 stage and ZRO4, and most 4 stage RO systems Includes the service manual "How to Service Your Reverse Osmosis System" by Dionicio Porras. ROFCTK, Filter change tool kit available separately. Service your RO like a pro.