The filters that we recommend that are compatible with the TGI WIN-455 are:

Stage 1: Sediment Prefilter 5 Micron - Liquatec SDF-25-1005 Sediment Filter
Stage 2: Carbon Block Prefilter KX Matrikx +CTO/2 Carbon Block 32-250-125-975
Stage 3: 50 gpd TFC Membrane GE Osmonics Desal TFM-50 Membrane
Stage 4: Inline 10" GAC Postfilter K2533 ** should be 1/4", but please double check your connection size.