LTWHOME Compatible Foam Sponge Filter Media Fits Laguna Pressure-Flo 2100 UVC Filter(Pack of 4) Contain 4 replacement foam filter rings. Custom designed and manufactured for Laguna Pressure-Flo 2100 UVC Filter. Enhances biological filtration. Provides efficient water flow with less clogging for long lasting filtration. Good for freshwater and saltwater environments.