Ensure peak mechanical filtration and crystal-clear pond water with genuine Laguna Pressure-Flo Replacement Foam Filter Rings (PT1738 / PT1507). Specially engineered for Laguna Pressure-Flo 3200 (PT1506) and Pressure-Flo 4000 (PT1728) pressurized pond filters, these high-density porous foam pads trap dirt, suspended algae, and organic sludge before water enters the UVC and biological chamber.