R 4087 -- 3.53X21.82 -- 2-212 B/UP NBR90

Back-up rings provide added extrusion resistance and prevent damage to O-rings and seals when subjected to high pressures, larger extrusion gaps, and/or high temperatures. The use of back-up rings can significantly increase the pressure rating of almost any seal. They are used in conjunction with O-rings or dynamic seals for both static and dynamic sealing applications. The cross section of a back-up ring is generally rectangular, and they are not designed for sealing purposes.