Back-up rings are the most common anti-extrusion
For 8400, 8500 & E4, E5 Series Rubber U-Cups & PolyPak Seals Piston & Rod for Pressures Over 800 psi
Because they are integrated with the seal, positively-actuated back-ups do not change the required axial groove width.
HS Profile static head seals are specified to replace the industry-standard o-ring and backup.