Sta-Rite Compatible System 3 S7M120 Modular Media 300 – Inner and Outer Replacement Filter. This BlueFlo model #BF-C008 modular filter set is compatible with Pentair Sta-Rite’s replacement filter cartridge kit for the System 3 S7M120. The set features a total of 300 square feet of filter area with one inner cartridge (100 square foot) and one outer cartridge (200 square foot). The cartridges are easy to clean and replace. The replacement filter cartridge kit is efficient at capturing fine debris, leaving you with clearer, cleaner pool water. Fits Pentair Sta-Rite System 3 S7M120 Modular Media 300 Filter. Small 100 square foot cartridge measures: 25-1/4″L x 8-1/2″D. Large 200 square foot cartridge measures: 18-1/2″L x 16-1/4″D.