Newer 50 GPD TFC Revised Seal Membrane used in Clack TFC-300, and TFC-400
S1764RS is used in the newer "50 gpd" models that look like Microline, but do not use this name, but instead has model number like the T.F.C. - 300 and - 400. Note: This is a common Microline / Clack Corporation 11 1/2" length replacement membrane.
Also used in WaterShield 50 ( Water Shield 50 )RO systems with S7028 and S7025 filters.
The 300 model would use S7028 and S7025 filters to go with this membrane.
The 400 model would include those, Plus the S7206W-JG as the 4th item.