produces Backup rings that are designed to keep O-Rings from extruding as well as Backup rings for U-Cups applications. These Back-up Rings are produced in either a contoured design, Split (MS28774) or Solid (MS27595) configuration and a wide range of materials are used to fit your application. You will find stock materials such as Fluorocarbon (FKM, Viton Fluorel), Hytrel, Nitrile (Buna-N), Polyether Ether Ketone (PEEK