This is a replacement o-ring for many types of in-line filters commonly used in spas and hot tubs. It sits between the lid and the body of the filter. It has a 149 mm (5 7/8") internal diameter and 159 mm (6 1/4") external diameter.

It fits the following filters:

• Rainbow RTL, RCF and RDC Series (notably PRB25, PRB35, PRB50 and PRB75)
• Sonfarrel pressure filters
• Waterway top-load filters
• Jacuzzi CFT and CFR series filters
• Hayward Micro Star Clear