5 stage reverse osmosis filter pack for Water Resources and International filter reverse osmosis systems. Includes 1 sediment, 1 carbon pre-filter, 1 carbon post-filter(canister type) and 1 inline GAC post-filter with 3/8 quick connect fittings (and 1/4″ adaptors), and 3 canister O-rings. Works with Envirotech and other 5 stage RO systems with 2 post filters. Includes the service manual “How to Service Your Reverse Osmosis System” by Dionicio Porras. Service your RO system like a pro!