HB90208 is an AS568-208 black Buna-N (Nitrile) 90 Shore A Back-Up Ring supplied with an inside diameter of 0.609 in (15.47 mm), a cross section of 0.139 in (3.53 mm), and an outside diameter of 0.887 in (22.53 mm). In service, this back-up ring allows a standard o-ring to operate at higher pressures than it could unsupported.
It resists propane and butane, many alcohols, and greases and lubricants. Buna-N (Nitrile) is widely chosen for an economical choice for high-volume maintenance programs and low compression set under sustained load. The material carries a published service range of -40°F (-40°C) to 250°F (121.1°C).
Maintenance and OEM teams specify it across fluid power, hydraulic and pneumatic systems, and automotive.
HB90208 ships individually. Unit weight is approximately 0.281 g. Application requirements vary, so validate compatibility with your process conditions prior to installation. If you need a size, durometer or compound that is not listed, APG can cross-reference from a print, a sample or a competitor part number.
Description 8-208 BLACK BUNA 90D BACK-UP RING
Actual Cross Section 0.139 inch (3.53 mm)
Actual Inside Diameter 0.609 inch (15.47 mm)
Actual Outside Diameter 0.887 inch (22.53 mm)
Measurement System Imperial
Product Category O-Rings - Backup Rings