8-255 BUNA 90 B/U RING

Use item HB90255 when a Buna-N NBR 90A Backup Ring is required for anti-extrusion support behind O-rings in high-pressure hydraulic and pneumatic glands. The item is specified by AS568-255; 5.609 inch (142.47 mm) ID x 0.139 inch (3.53 mm) CS; 5.887 inch (149.53 mm) OD, with 5 5/8 inch nominal ID; 1/8 inch nominal CS for cross-reference against common gland and replacement dimensions. The Buna-N nitrile (NBR) construction supports oil, grease, fuel and general hydraulic fluid resistance in common industrial equipment. It is with a listed temperature range of -40°F (-40°C) to 250°F (121°C), which can help narrow material selection for heat, cold or process exposure. The black color and round profile provide a practical visual identifier during receiving, stocking and installation. As a backup ring, it works with a primary O-ring to help limit extrusion into clearance gaps under pressure. The each-unit format supports precise replacement, kitting, resale and job-specific purchasing. Important product identifiers include O-rings, replacement seals, fluid sealing, material compatibility and dimensional fit. It supports customer comparison, distributor cataloging and specification-based selection without relying on pricing, availability or shipping claims.