8-439N90

8-N90 back-up rings are molded from 90A durometer nitrile (Buna-N) and provide excellent resistance to grease, petroleum fluids, and motor oil. Designed to prevent O-ring extrusion in high-pressure applications, these Parbak®-style rings feature a dished cross-section that ensures uniform contact with the O-ring while the flat surface faces the extrusion gap. They stretch for easy installation and quickly return to their original size. Sized to standard AS568 O-ring dash numbers, these back-up rings offer reliable performance in both static and dynamic sealing applications.

• Enhances O-ring performance in high-pressure applications
• Resists grease, petroleum fluids, and motor oil
• Parbak®-style dished design offers uniform contact with the O-ring
• Stretches for easy insallation
• Compatible with standard AS568 O-ring dash numbers