The Pentair 300 SqFt S7M120 Inner and Outer Cartridge Pack is a replacement filter cartridge kit designed for the Pentair Sta-Rite System 3 S7M120 Modular Media Pool Filter. It includes one smaller inner cartridge (100 sq ft) and one larger outer cartridge (200 sq ft).  

Here are the key features:

• Compatibility: Fits Pentair Sta-Rite System 3 S7M120 Modular Media 300 Filter.  
• Dimensions:
  • Small cartridge: Approximately 25-1/4"L x 8-1/2"D.
  • Large cartridge: Approximately 18-1/2"L x 16-1/4"D.
• Function: Efficiently captures fine debris, leaving clearer and cleaner pool water.  
• Replacement for: Sta-Rite 25021-0200S & 25022-0201S System 3 S7M120 Set, Darlly Sr300.