The model SST-FLTR was an replacement unit for a failed (leaking tank) SST-FLTR unit. The new unit I installed came with a different filter than the previous one so I ended up having to do a lot more work than I had anticipated. If I had investigated further I believe that I could have purchased the same filter that came with the previous unit and saved myself a good deal of extra work. The previous filter was an F-601R and the new unit came with an F-1000. Different hoses/connections.