API Filstar XP Filtration 20 PPI Filter Pads are replacement parts for API Filstar XP Canister Filters. The filter pads are designed to be used in the lowest part of the filter's chamber, directly below the 30 PPI filter. Filstar XP 20 PPI Filtration Pads mechanically filter particles, waste and uneaten food from the water. The filters feature an open-cell design that effectively catches contaminates without impeding water flow or becoming easily clogged. The 2-piece package works to keep water clean and clear for approximately 3 months.