90A Durometer Urethane Back-Up Rings -015 Dash Size, Per Pack

For urethane back-up rings like these, stretching them over the O-ring groove is pretty much a hand operation. The 90A durometer urethane is firm enough to hold its shape once seated but flexible enough that you can work it into place without needing special tooling. Once stretched and released, it returns to its original size quickly, which helps it sit correctly in the groove without a lot of fussing around.

These urethane back-up rings can operate in temperatures from -65°F to 220°F.