The Laguna PT1505 is the correct replacement filter for the following:
The Pressure-Flo Replacement Foam for PT1504 - 4 pack is replacement foam kit for the Laguna Pressure-Flo 2100 and 8000 models that includes 4 replacement foam filter rings. These replacement foam filters help remove debris from pond water through its porous media. Laguna foam filters can be installed easily and are not difficult to maintain. Be sure to replace these water pump foam filters annually for optimum performance.
Pressure-Flo Replacement Foam for PT1504 - 4 pack specifications: