Back-up Ring Type BU is a rectangular, uncut support ring used to prevent seal extrusion in high-pressure applications. Designed for static and dynamic systems, it is installed behind O-Rings or other primary seals. Made from durable materials like PTFE or elastomers, the BU ring enhances sealing performance, extends service life, and ensures reliable operation in hydraulic and pneumatic environments. This is a Custom Article Number with a Customer Specific Design.