Always have the backup ring you need for oily equipment operating at pressures up to 2,500 psi. These rings support O-rings to extend their life and prevent them from deforming under pressure, which can cause pressure loss. Made of Buna-N, they won’t swell when exposed to grease, petroleum fluids, and motor oil. However, they will degrade when exposed to mild or harsh chemicals. They’re often used in hydraulic and automotive systems.