The Sta-Rite 21" Tank O-Ring (System:3) - 24850-0008 is a replacement O-ring designed to create a watertight seal for Sta-Rite System 3 pool and spa filters. Here's a breakdown of its key features:  

• Purpose:
  • It's designed to seal the tank of Sta-Rite System 3 filters, preventing leaks.
• Compatibility:
  • This O-ring is compatible with various Sta-Rite System 3 models, including:
    • Modular Media SM Series Pool/Spa Cartridge Filters (e.g., S7M120, S7M400)  
    • SD Series Pool/Spa D.E. Filters (e.g., S7D75)  
    • Sand filter models such as S7S50.  
• Dimensions and Material:
  • It's a 21-inch O-ring, designed to fit the specific dimensions of the Sta-Rite System 3 tanks.  
  • It is made of rubber.
• Function:
  • Ensures a proper seal to maintain optimal filter performance.

Essentially, this O-ring is a vital replacement part that helps keep your Sta-Rite System 3 pool filter functioning correctly and efficiently.